EXCHANGE 


•P 


Rearrangements  of  Some  New  Hydroxamic 

Acids  Related  to  Heterocyclic  Acids, 

and  to  Diphenyl-  and  Triphenyl- 

Acetic  Acids 


EXCHANGE 

1922 


CHARLES  DEWITT  KURD 


Rearrangements  of  Some  New  Hydroxamic 

Acids  Related  to  Heterocyclic  Acids, 

and  to  Diphenyl-  and  Triphenyl- 

Acetic  Acids 


A  DISSERTATION 
PRESENTED  TO  THE 

FACULTY  OF  PRINCETON  UNIVERSITY 

IN  CANDIDACY  FOR  THE  DEGREE 

OF  DOCTOR  OF  PHILOSOPHY 

BY 


CHARLES  DEWITT  KURD 

\x 


E ASTON,  PA.: 

ESCHENBACH  PRINTING  COMPANY 
1922 


REARRANGEMENTS  OF  SOME  NEW  HYDROXAMIC  ACIDS  RE- 
LATED TO  HETEROCYCLIC  ACIDS  AND   TO  DIPHENYL-  AND 
TRIPHENYL-ACETIC  ACIDS. 

A  summary  of  the  serious  attempts  to  explain  the  mechanism  of  the 
Beckmann  rearrangement  must  necessarily  include  the  work  of  Hooge- 
werff  and  van  Dorp,1  Hantzsch,2  Stieglitz,3  and  Jones.4'5  The  types  of 
compounds  generally  assumed  to  undergo  this  rearrangement  are  the 
azides,  mono-substituted  /3-hydroxylamines,  monobromo-amines,  oximes, 
amidoximes,  oximido  acid  esters,  acid  halogen  amides  and  the  hydroxamic- 
acid  derivatives.  The  azides  are  assumed  to  decompose  as  follows : 

R— CO— N:N«   >  R— CO— N:  +  N,  — >  R— N:C:O 

R— CHr-N :  N, >  R— CH«—N :  +  N, >  R— N :  CH,. 

These  two  cases,  together  with  the  mono-substituted  /3-hydroxylamines 
presented  below,  furnish  examples  of  the  Beckmann  rearrangement  that 
have  never  been  explained  successfully  except  by  the  theory  of  Stieglitz  and 
of  Jones. 

(O,H6)3C— NHOH  — >  (C«H6),C— N:  +  H,O  — >  (C«H6)jC  :NC«H6. 

Stieglitz  was  the  first  investigator  to  propose  the  hypothesis  that  univa- 
lent  nitrogen  derivatives  form  the  primary  decomposition  products  in  these 
rearrangements.  His  extensive  experimental  work  has  demonstrated  the 
soundness  of  this  postulate.6  Some  years  later,  Jones  formulated  the 
reaction  mechanism  in  a  detailed  manner  by  applying  the  theory  of  elec- 
tron valence  to  the  interpretation  given  by  Stieglitz.  The  electron  mechan- 
ism was  represented  as  follows.4'5 

O 

R  +-C+-N  +  — ^-[OC+tN-+R]  — >-  OCJZN-+R. 

Unless  there  were  a  driving  force  acting  to  cause  the  transfer  of  the 
radical  from  carbon  to  nitrogen,  it  would  still  be  difficult  to  imagine  why  the 

1  Hoogewerff  and  van  Dorp,  Rec.  trav.  chim.,  6,  373  (1887) ;  8,  173  (1889). 

2  Hantzsch,  Ber.,  35,  228,  3579  (1902);  ibid.,  27,  1256  (1894). 

3  Stieglitz,  Am.  Chem.  J.,  18,  75  (1896);  29,  49  (1903);  Stieglitz  and  Earle,  30,  399, 
412  (1903);  Stieglitz  and  Leech,  J.  Am.  Chem.  Soc.,  36,  272  (1914);  etc. 

«  Jones,  Am.  Chem.  /.,48,  1  (1912);  50,  414  (1913). 

5  /.  Am.  Chem.  Soc.,  36, 1268  (1914);  etc. 

6  The  rearrangement  of  ketoximes,  which  was  originally  attributed  by  Stieglitz 
to  the  formation  of  univalent  nitrogen  derivatives,  is  now  regarded  as  an  exception. 
His  present  view  assumes  "the  rearranging  power  of  an  intermediate  hydrochloride  of 
a  univalent  nitrogen  derivative,  acting  in  place  of  the  ordinary  free  univalent  nitrogen 
compound."     See  Montagne   (Ber.,  43,  2015  (1910)),  Schroeter   (ibid.,  44,  1207  (1911)), 
and    Stieglitz. 


REARRANGEMENTS  OF  NEW 


2423 


reaction  should  proceed,  even  with  the  explanation  offered.  Such  a  driv- 
ing force  is  to  be  found  in  the  shifting  of  electrons  within  the  molecule. 
Jones  stressed  particularly  that  the  free  valences  of  univalent  nitrogen 
afforded  the  ''stage  setting  required  to  furnish  a  suitable  environment  in 
which  the  essential  action,"  viz.,  the  transfer  of  the  radical  from  carbon  to 
nitrogen  might  take  place.  In  a  footnote  to  an  article  published  some 
months  later,3  Stieglitz  stated  that,  in  regard  to  the  most  fundamental 
questions  of  these  rearrangements  "postulating  a  shifting  of  electrons  from 
carbon  to  nitrogen,  and  a  migration  of  a  positive  radical,  Professor  Jones 
and  the  writer  are  happily  in  entire  agreement." 

As  viewed  from  present  day  standards,  this  interpretation  with  very 
slight  modifications,  still  holds.  In  late  years,  worthy  evidence7  has  been 
submitted  to  show  that  the  positive  charges  possessed  by  an  atom  are 
centered  in  its  nucleus.  In  compounds  which  are  formed  by  the  sharing 
of  negative  electrons,  a  "bond"  consists  of  a  pair  of  electrons  held  in  com- 
mon between  two  atoms.  This  theory  of  a  chemical  bond  requires  sym- 
bols in  which  positive  charges  cease  to  appear,  except  as  they  form  an 
integral  part  of  the  nucleus  of  any  atom.  Such  an  interpretation  would 
mean  simply  that  a  symbol,  Ct+N,  employed  at  a  time  when  ion  charges, 
rather  than  electrons  in  the  present  sense,  held  the  attention  of  chemists, 
would  now  become  C  :  N ;  that  is,  the  carbon  atom  and  the  nitrogen  atom 
share  a  single  pair  of  electrons.  This  conception  of  paired  electrons  would 
account  just  as  readily  for  the  driving  force  necessary  to  bring  about 
rearrangement.  Thus,  the  system  of  symbols  C  :  N  — >  C  :  N  is 
equivalent  to  C*+N  — >  C+IN  previously  employed. 

Possibly  the  formula  C+ZN  contains  an  assumption  not  necessarily 
implied  by  the  formula  C  :  N  in  which  two  pairs  of  electrons  are  shared, 
since  the  former  suggests  that  a  compound  which  contains  such  a  group 
would  not  be  exactly  non-polar,  although  it  should  not  be  regarded  as 
polar  in  the  sense  in  which  Na+  Cl~  must  be.  To  meet  difficulties  of  this 
kind,  Lewis  employs  formulas  in  which  the  pairs  of  electrons  are  placed 
nearer  one  symbol  than  another,  e.  g.,  A  :  B,  which  implies  that  the  mole- 
cule AB  shows  some  polar  characteristics.  With  these  modifications  to 
adapt  the  old  electronic  formulas  to  present  day  practices,  equations  may 
be  given  to  represent  the  rearrangement  of  a  univalent  nitrogen  deriva- 
tive of  a  hydroxamic  acid. 

Formulas  I,  la  and  Ib  represent  the  intermediate  univalent  nitrogen 
derivative;  Formulas  II,  Ila  and  116  represent  a  transition  stage,  the  re- 
arrangement of  the  positive  radical,  R.  It  will  be  noted -that,  in  Formula 
II,  although  the  carbon  atom  still  has  its.  "octet"  completed,  the  nitrogen 
atom  has  only  6  electrons  in  the  outer  shell.  By  the  sharing  of  electrons, 
both  the  nitrogen  and  the  carbon  atoms  may  complete  their  octets.  This 
7  G.  N.  Lewis,  Langmuir  and  others. 


2424      7 

:  •    R 


,W-  JOXES  AND  CHARLES  D.  KURD. 


n 

Fig.  1. 


A    A 

/ 

">->R 

/     /\ 

7          /!  A    A    A 

A.--.  .__x.  

/ti     /  c 

/ 

/      \ 

/  Q            /   Q 

/      /          ''"°     /°     /'N    / 

i 

"N    / 

£  An 

r 

n- 

Fig.  2. 

m0 

R 

_.+  t+^.^      .-     .+    _+     __^ 

(16).  (116).  (Illfc). 

is  represented  in  Formulas  III,  Ilia  and  III6,  the  isocyanate  stage  in  the 
rearrangement. 

With  this  conception,  it  is  easy  to  understand  why  the  radical  R  is  able 
to  part  company  with  carbon  and  attach  itself  to  nitrogen.  No  hypothe- 
sis has  been  offered,  however,  to  explain  why  one  radical  R  will  do  so  with 
much  greater  readiness  than  some  other  radical  R'.  To  seek  an  explana- 
tion of  this  factor  was  one  of  the  motives  that  prompted  the  work  which 
follows. 

Chief  interest  in  the  present  paper  centers  upon  the  reactions  of  dihy- 
droxamic  acids.  They  have  been  shown  to  rearrange  in  the  following  man- 


ner. 


R— CO— NH— OCOR ' 


[R— CO— N]    +  R'— COOH 

— >   R— N   =   C  :O  +  R'— COOH. 


Either  the  action  of  heat,  or  of  warm  solutions  of  alkalies,  will  produce 
this  effect.  In  the  former  case,  the  isocyanate  is  formed  by  dry  distillation 
of  the  dihydroxamic  acid,  or,  preferably,  by  heating  a  salt  of  the  acid. 
Usually  there  is  a  fairly  definite  temperature  at  which  the  decomposition 
of  the  dry  salt  takes  place.  However,  certain  cases  have  proved  that  it 
is  not  a  reliable  method  to  use  when  two  similar  compounds  are  to  be  judged 
for  comparative  ease  of  rearrangement.  If  solutions  rre  employed,  the 
isocyanate  generally  reacts  immediately  with  waiter  to  form  the  amine,  or 
the  corresponding  disubstituted  urea.  The  behsvior  of  neutral  solutions 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2425 

of  the  sodium  or  of  the  potassium  salts  in  water  seems  now  to  furnish  a 
more  accurate  criterion  by  which  to  judge  the  ease  of  rearrangement  of 
these  particular  compounds 

A  few  years  ago,  phenyl-acethydroxamic  acid9  was  studied.  The 
benzoyl  ester  of  this  acid  was  capable  of  forming  salts  which  possessed 
unusual  instability  towards  heat.  Its  solid  potassium  salt  suffered 
Beckmann  rearrangement  spontaneously  at  room  temperature.  Here, 

C6H5CH2CO— NK— OCOC6H5  — >   C6H5CH2— NCO  +  C6H5COOK. 

Because  of  this  rearrangement,  it  was  not  found  possible  to  form  a  clear 
solution  of  the  salt  in  water,  unless  it  was  prepared  immediately  after  the 
isolation  of  the  salt.  We  have  recently  repeated  this  experiment,  and 
found,  in  addition,  that  the  clear  solution,  when  left  at  room  temperature 
for  2  hours,  did  not  undergo  a  noticeable  rearrangement.  A  small  white 
precipitate  of  the  urea  collected  in  10  hours,  however.  The  similar  po- 
tassium salt  of  the  benzoyl  ester  of  acethydroxamic  acid,  CH3 — CO — 
NK — OCOCeHs,  did  not  possess  this  marked  tendency  to  rearrange;  so 
the  replacement  of  hydrogen  by  phenyl  must  have  occasioned  the  decrease 
in  stability.  With  this  in  view,  diphenyl-  and  triphenyl-acethydroxamic 
acid  were  deemed  important  compounds  to  study.  The  sodium  or  the 
potassium  salts  of  their  acyl  esters  should  exhibit  <a  greater  capacity  for 
rearrangement  in  solution  than  the  similar  compounds  in  the  monophenyl 
series. 

The  univalent  nitrogen  compounds,  [R — CO — N],  which  have  been 
assumed  to  be  the  primary  products  of  decomposition,  have  never  been 
isolated.  The  isocyanates,  resulting  from  rearrangements  which  involve 
readjustments  of  electrons,  are  obtained  instead.  It  was  not  our  object 
in  this  investigation  to  try  to  isolate  such  derivatives.  Indeed,  with  the 
groupings  [(C6H5)2CH— CO— N],  and  [(C6H5)3C— CO— N]  the  tendency 
to  rearrange  to  form  isocyanates  should  be  greater  than  in  any  case  pre- 
viously studied. 

Tripheny]  methyl  is  a  group  that  is  known  to  display  a  tendency  to 
exist  as  a  free  radical.  Certainly,  then,  it  would  seem  highly  probable 
that  a  derivative  such  as  [(C6H5)3C — CO — N],  would  be  far  more  apt  to 
separate  momentarily  into  [(C6H5)3C — ]  and  [ — CO — N]  than  a  group  such 
as  [H3C — CO — N  ]  in  which  the  linking  of  carbon  to  carbon  is  conceived 
to  be  stronger.  The  latter  would  give  rise  to  [H3C] —  and  [ — CO — N]. 
By  no  means  must  it  be  considered  probable  that  free  radicals  dis- 
playing the  great  order  of  reactivity  shown  by  triphenylmethyl  could 
ever  be  isolated  while  in  the  presence  of  the  highly  reactive  univalent 
nitrogen. 

As  a  result  of  earlier  experiments,  and  of  those  included  in  this  article, 
9  Thiele  and  Pickard,  Ann.,  309.  189  (1899):  Jones,  Am.  Chem.  /.,  48,  6  (1912). 


2426  LAUDER  W    JONES  AND  CHARLES  D.  KURD. 

we  were  led  to  formulate  an  hypothesis  which  may  be  stated  as  follows: 
the  relative  ease  of  rearrangements  of  the  Beckmann  type  is  dependent 
upon  the  tendency -for  the  radical  R,  in  the  univalent  nitrogen  derivative, 
e.  g.,  [R — CO — N],  to  exist  as  a  free  radical. 

It  must  be  noted  that  this  hypothesis  does  not  deal  with  the  ease  of 
formation  of  the  univalent  nitrogen  compound.  It  is  essential  that  the 
group  —  NHX  in  the  original  molecules,  R — CO — NHX,  be  identical 
when  two  different  compounds  are  compared.  An  extreme  case  of  the 
effect  produced  when  different  groups  are  substituted  is  displayed  in  the 
acyl  alkyl  halogen  amines,  e.  g.,  R — CO — NCI — C&Hn.  Stieglitz  observed 
that  compounds  of  this  type  show  no  tendency  to  undergo  rearrangement.9 

Triphenyl methyl,  and  other  groups  that  are  known  to  exist  free,  have 
been  shown  to  "exhibit  polar  characteristics  in  many  of  their  compounds. 
For  example,  triphenylmethyl  bromide  displays  marked  conductivity 
when  dissolved  in  sulfur  dioxide;10  this  is  one  of  the  arguments  which 
leads  to  the  belief  that  an  ion,  or  a  pseudo-ion,  (Cel^sC*,  must  exist  in 
the  solution.  Furthermore,  it  has  been  shown  that  triphenylmethyl  is 
formed  in  the  cathode  chamber  when  triphenylmethyl  bromide  is  elec- 
trolyzed.  In  fact,  appropriate  solutions  of  triphenylmethyl,  itself,  conduct 
the  electric  current.11  These  are  important  facts  in  support  of  our 
hypothesis. 

From  the  standpoint  of  our  hypothesis,  it  would  seem  that  the  tendency 
for  the  phenylmethyl  radical,  CeH5 — CH2,  to  exist  free  is  greater  than  for 
methyl,  CH3.  The  allusion  is  to  the  experimental  fact  that  the  deriva- 
tives of  phenyl-acethydroxamic  acid  suffer  rearrangement  more  easily 
than  those  of  acethydroxamic  acid.  On  the  basis  of  this  hypothesis,  also, 
the  observation  made  by  McCoy  and  Stieglitz,12  and  supplemented  by 
van  Dam,13  that  dibromo-salicylic-bromo-amide  rearranges  even  at  —12°, 
is  evidence  for  the  tendency  of  the  radical  C6H2Br2.OH  to  exist  free.  Other 
bromo-amides  that  have  been  studied  exhibit  a  more  stable  character. 

From  this  same  standpoint,  it  may  be  predicted  that  any  substituted 
acethydroxamic  acid  containing  a  tri-aryl  methyl  group  will  undergo 
rearrangement  with  great  ease.  For  example,  tri-bisphenyl-acethydrox- 
amic  acid,  (C6H5— C6H4— )3C— CO— NHOH,  should  form  derivatives 
that  are  even  more  unstable  than  triphenyl-acethydroxamic  acid.  The 
group  tribisphenylmethyl,  in  contrast  to  triphenylmethyl,  is  one  that 
has  been  shown  to  exist  exclusively  in  the  monomolecular  form  at  room 

9  Stieglitz,  Am.  Chem.  J.,  29,  49  (1903). 

10  Gomberg,  Ber.,  35,  2397  (1902). 

11  Gomberg  and  Cone,  ibid.,  37,  2403  (1904);  Schlenk,  Weichel,  and  Herzenstein. 
Ann.,   372,   10   (1910). 

18  McCoy  and  Stieglitz,  Am.  Chem.  J.,  21,  116  (1899). 

13  Van  Dam.  Rec.  trav.  Mm.,  18,  408  (1899);  19,  318  (1900) 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2427 

temperature.14  Therefore,  in  the  univalent  nitrogen  derivative,  [(C6H5 — 
CeH4 — )sC — CO — N],  there  should  be  a  pronounced  tendency  for  the 
momentary  existence  of  tribisphenylmethyl,  and  the  ultimate  formation 
of  the  isocyanate. 

The  applications  of  this  hypothesis  need  not  be  restricted  to  one  class 
of  radicals  that  show  a  tendency  to  exist  free.  Since  certain  radicals 
which  contain  divalent  nitrogen18  have  been  prepared,  a  hydroxamic  acid 
which  could  furnish  such  a  group  might  also  rearrange  with  considerable 
ease.  Illustrations  would  be, 

(CeHsW— CO— NHOH  >    (C6H5)2N— N:  C:O+H2O. 

(CH3O— C6H4)2N— CO— NHOH  — >    (CH3O— C6H4)2N— N :  C :  O  +H2O. 

Benzophenone  when  it  is  treated  in  ether  solution  with  potassium 
develops  an  intense  color.16  Since  the  boiling  point  of  the  ether  is  un- 
changed after  complete  solution  of  the  metal,  a  trivalent  carbon  radical, 
(CeHs^CXOK) — ,  is  assumed  to  exist  in  solution.  In  this  connection, 
therefore,  the  hydroxamic  acid  of  benzilic  acid,  (C6H5)2C(OH).CO.NHOH, 
should  present  a  somewhat  complicated,  but,  nevertheless,  a  highly  inter- 
esting case  to  develop.17 

Our  assumptions  were  corroborated  to  a  large  extent  by  the  experi- 
mental evidence  submitted  in  this  paper.  Unexpected  difficulties  presented 
themselves  in  the  attempts  to  prepare  the  sodium  and  potassium  salts  in 
the  diphenyl-acethydroxamic  acid  series.  If  the  customary  procedure, 
viz.,  the  addition  of  an  alcoholic  solution  of  sodium  ethylate  to  an  alcohol- 
ether  solution  of  the  benzoyl  ester  of  the  acid,  e.  g.,  (C6H5)2CH — CO — 
NH — OCOC6H5,  was  followed,  no  precipitation  of  the  salt  occurred,  even 
when  a  very  large  excess  of  ether  was  used.  The  existence  of  the  salt  in 
solution  was  proved,  but  the  salt  could  not  be  obtained 'pure.  Evapora- 
tion of  the  alcohol  and  ether  in  VQCUO  always  left  a  mixture  of  the  salt  with 
its  products  of  decomposition  and  rearrangement;  viz.,  diphenylmethyl 
isocyanate,  diphenylmethyl  urethane,  sodium  benzoate  and,  also,  sym. 
bi-diphenylmethyl  urea,  if  any  water  was  present.  When  this  residue  was 
extracted  with  cold  water,  and  the  solution  filtered  and  boiled,  there  was 
an  immediate  precipitation  of  some  sym.  bi-diphenylmethyl  urea,  which 
is  the  normal  reaction  for  salts  of  this  character. 

Similar  difficulties  arose  in  the  study  of  triphenyl-acethydroxamic 
acid.  The  sodium  or  the  potassium  salts  of  the  benzoyl  ester  could 
not  be  formed  pure.  The  acetyl  ester  seemed  to  yield  a  potassium 

14  Schlenk,  Weichel  and  Herzenstein,  Ann.,  372,  11  (1910). 

16  Wieland,   "Die  Hydrazine,"  F.  Enke,  Stuttgart,  1913,  p.  73. 

16  Schlenk  and  Thai,  Ber.,  46,  2843  (1913);  Schlenk  and  Weichel,  ibid.,  44,  1183 
(1911). 

17  Jones  and  Neuffer  (J.  Am.  Chem.  Soc.,  39,  659   (1917)),  have  studied  the  re- 
arrangements of  lact-hydroxamic  acid,  Ch3 — CHOH — CO — NHOH,  and  of  mandel-hy- 
droxamic  acid,  C6H5CH(OH).CO.NHOH. 


2428  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

salt  insoluble  in  ether;  but  subsequent  tests  showed  that  it  was  mixed 
to  a  large  extend  with  triphenylmethyl  isocyanate.  This  isocyanate, 
not  previously  described,  possesses  a  remarkable  stability,  even  in  the 
presence  of  boiling  water.  Thus,  when  the  precipitate  containing  the 
potassium  salt  was  taken  up  in  water,  and  heated,  only  the  isocyanate 
separated.  The  cause  of  its  sluggishness  may  be  attribu,  ed  to  its  insolu- 
bility in  water.  It  reacts  normally  with  aniline  in  ether  to  form  the  urea 
derivative. 

(C«H,),C— NCO+C.HJNH2  — >  CJI6— NH— CO— NH— C(C«H6),. 

The  evidence  obtained  proves  that  there  is  an  increase  in  the  ease  of 
rearrangement  of  the  molecule  as  more  phenyl  groups  are  added.  In 
solution,  the  potassium  salt  of  the  benzoyl  or  acetyl  ester  of  monophenyl- 
acethydroxamic  acid  was  comparatively  stable  at  room  temperature;  a 
similar  solution  of  the  diphenyl  compound  became  turbid  in  a  short  time ; 
whereas  the  triphenyl  derivative  showed  rearrangement  almost  immediately 
when  it  was  treated  with  water.  In  the  diphenyl  or  in  the  triphenyl  series, 
it  was  found  to  be  impossible  to  obtain  a  sodium  or  a  potassium  salt  which 
failed  to  show  the  effects  of  extensive  decomposition.  For  this  reason, 
the  temperature  of  decomposition  of  the  pure  dry  salts  could  not  be 
determined  accurately. 

The  silver  salts,  made  by  the  action  of  aqueous  silver  nitrate  upon  the 
cold  ether  solutions  of  the  sodium  or  potassium  salts  were  somewhat  solu- 
ble,19 but  precipated  for  the  most  part.  Chromo-isomerism  was  dis- 
played here.  The  silver  salt  of  the  benzoyl  ester  of  diphenyl-acethydrox- 
amic  acid,  when  first  formed,  was  bright  yellow.  In  a  short  time,  the 
yellow  substance  changed  to  a  pure  white  salt.  The  similar  salt  in  the 
triphenyl  series  precipitated  as  a  white  solid,  but  changed  soon  to  a  brilliant 
yellow  salt.20 

19  The  exact  cause  of  the  solubility  of  the  sodium  and  of  the  potassium  salts  in 
alcohol  with  a  large  excess  of  ether  is  purely  a  matter  of  conjecture.  There  may  be 
tautomeric  forms,  one  soluble  and  the  other  insoluble,  such  as  (CeH6)jCHC — O — NK — 
OCOCH,  and  (C«H6)tCH— C  (OK):  N— OCOCH,.  It  may  be  caused  by  the  addi- 
tion of  a  molecule  of  alcohol;  thus,  (C»H6)CH— C(OK)(OC2H6)— NH— OCOCH3. 
These  are  suggestions,  which  may  be  correct.  Salts  of  the  alkali  metals  which  are 
soluble  in  ether  are  very  uncommon  but  not  unknown.  Sodium  iodide  behaves  in  this 
manner.  Loeb,  /.  Am.  Chem.  Soc.,  27,  1020  (1905). 

ao  There  are  many  chromo-isomers  on  record;  such,  for  example,  as  silver  violurate 
(Hantzsch,  Ber.,  42,  969  (1909);  Henrich.  "Theorien  der  Org.  Chem.,"  1918,  p.  364) 
which  is  colorless  when  precipitated,  and  gradually  changes  through  green  to  a  dark 
brown.  Titherlcy  (.7  Chem  Soc.,  71,  468  (1897);  79,  408  (1901)),  reported  silver 
benzamide  to  t-xist  in  an  orange  and  in  a  white  modification.  Jones  and  Oesper  J.  Am. 
Chem.  Soc..  36,  2208(1914)),  found  chromo-isomeric  silver  salts  among  acyl  derivatives 
ofhydroxy-urethanes;  c.  g.  C6H6CO— O— NAg— CO— OR.  These  salts,  yellow  when 
prepared  were  easily  transformed  into  white  modifications,  especially  if  R  represents 
i.w>-l>utvl.  /.vo-amvl.  or  benzyl. 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2429 

Although  the  salts  of  the  alkali  metals  could  not  be  isolated  pure,  solu- 
tions of  them  in  water  could  be  obtained  without  extensive  decomposition, 
if  the  silver  salts  were  suspended  in  an  ice-cold  solution  of  potassium  bro- 
mide. In  a  few  hours  the  reaction  was  complete.  This  constitutes  a 
helpful  modification  of  a  reaction  never  before  applied  to  hydroxamic 
acids. 

An  interesting  relationship  between  chemical  constitution  and  melting 
points  is  to  be  gained  from  a  study  >of  the  following  .table.     The  low  melting 
benzoyl  ester  of  triphenyl-acethydroxamic  acid  is  of  particular  interest 
(See  experimental  part,  p.  2439.) 

M.  Pt.  Benzoyl  ester.  Difference. 

°c.  °c.  «c. 

CH3CO— NHOH                         87  69  or  98  18  or +11 

C6H6CH2CO— NHOH               145                          120  25 

(C6H5)2CH— CO— NHOH        173                         140  33 

(C6H5)3C— CO— NHOH           178  44-47  131-134 

Two  new  methods  of  preparation  of  hydroxamic  acids  were  investigated. 

First,  the  action  of  free  hydroxylamine  upon  a  ketene.     With  diphenyl 

ketene,   the  compound  formed  was  diphenyl-acethydroxamic  acid,   the 

same  in  every  respect  as  that  prepared  by  other  means.     The  equation  is 

(C6H5)2C:CO  +  NH2OH  —+  (C6H5)2C-C  :O 

I       I 
H    NHOH. 

The  reaction -is  perfectly  analogous  to  the  addition  of  ammonia,  or  amines, 
to  ketenes,  R2C:  CO  +  H— NHR' — ^R2CH— CO— NHR'.  Staudinger21 
•predicted  the  formation  of  hydroxamic  acids,  but  stated  "Die  Einwirkung 
von  Hydroxylamine,  die  zur  Bildung  von  Hydroxamsauren  fiihren  sollte, 
ist  noch  nicht  untersucht." 

There  is  another  possible  direction  in  which  hydroxylamine  might  add 
to  diphenyl  ketene.  The  amide  of  benzilic  acid  would  be  formed ;  (C6H5)2- 
C:CO  +  NH2OH  — **  (C6H5)2C(OH)— CONH2.  There  are  no  cases 
recorded  in  which  the  hydroxyl  group  adds  to  ketenes  in  such  a  manner. 
Invariably,  it  combines  with  the  carbonyl  group.  Hydrogen  peroxide, 
similar  in  many  respects  to  hydroxylamine,  would  be  forced  to  add  hydroxyl 
and  form  benzilic  acid,  if  there  were  addition  at  all.  However,  Nicolet  and 
Pelc22  recently  reported  that  the  amount  of  benzilic  acid  formed  when 
the  two  were  mixed  in  anhydrous  solvents  was  no  greater  "than  when  the 
ketene  itself,  without  the  addition  of  peroxide  was  treated  in  the  same  way." 
In  the  light  of  these  results,  it  is  not  at  all  surprising  that  no  trace  of  the 
amide  of  benzilic  acid  was  found. 

A  profitable  field  of  research  is  made  possible  by  this  reaction.  For 
example,  such  ketenes  as  diphenylene  ketene,  (CiaH8):C:CO;  methyl 
21  Staudinger,  "Die  Ketene,"  F.  Enke,  Stuttgart,  1912,  p.  36. 

»2  Nirnlpf  and  Pplr.    T    A  m    C.hc.m    Snc  .  43.  935  C1Q21V 


2430  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

vinyl  ketene,  CH2  :  CH— C(CH3)  :  CO;  ethyl  ketene  carboxylic  ester, 
OC  :  C(C2H5)— COOC2H5;  carbon  suboxide,  C3O2;  and  ketene,  itself, 
with  hydroxylamine,  or  substituted  hydroxylamines,  should  lead  to  inter- 
esting results. 

The  second  new  method  of  preparing  hydroxamic  acids  is  a  modification 
of  the  long  established  method  in  which  acid  chlorides  are  employed. 
Heretofore,  the  chloride  has  been  allowed  to  act  upon  an  aqueous  solution 
of  hydroxylamine.  This  always  leads  to  side  reactions,  which  lower  the 
yield  and  augment  the  difficulty  of  purification  of  the  desired  product. 
When  the  acid  chloride  was  dissolved  in  a  neutral  solvent,  such  as  benzene, 
and  a  trifle  more  than  2  mols  of  free  hydroxylamine  was  added,  it  was 
found  that  a  quantitative  yield  of  monohydroxamic  acid  resulted. 

(C6H6)8C—  COC1+NH,OH  — >  (C,H6)3C— CO—  NHOH  +  NH,(OH)C1. 
This  reaction  was  modified  later  so  that  the  preparation  of  free  hydroxyl- 
amine was  avoided.  Two  equivalents  of  pyridine  or  of  sodium  carbonate 
crystals  was  used  with  one  equivalent  of  hydroxylammonium  chloride 
in  a  benzene  or  an  ether  solution  of  the  acid  chloride.  A  quantitative 
yield  was  obtained  here  also. 

Two  heterocyclic  hydroxamic  acids  were  studied,  one  a  deriva- 
tive of  furane,  and  the  other  of  thiophene.  The  former  (I)  will  be  called 

l|^  Jl  — CO— NHOH  ^  JJ  — CO— NHOH  / 

O        (I).  S        (II). 

pyromucyl-hydroxamic  acid ;  and  the  latter  (II),  a-thenhydroxamic  acid.22 
Previous  work  with  heterocyclic  hydroxamic  acids  is  very  slight.  Pyro- 
mucyl-hydroxamic acid  was  prepared  by  Pickard  and  Neville23,  and  by 
Rimini,24  but  was  not  extensively  studied.  A  few  isolated  examples  in  the 
pyrone  series  are  known.25  Awto-ethyl-thenhydroximic  acid,  C4H3S — 
C(OC2H5)  :  NOH,  has  been  studied  by  Douglas.28  It  was  not  found  possi- 
ble to  isolate  this  in  the  syn  form.  One  object  or  our  investigation  was  to 

22  Other  names  such  as  a-thienyl  formhydroxamic  acid,  or  a-thenoyl-/3-hydroxyl- 
amine  suggest  themselves.  Both  of  these  names  have  their  shortcomings.  Essentially, 
the  compound  is  a  derivative  of  thiophene,  not  of  formhydroxamic  acid;  to  call  it  a 
"hydroxylamine,"  conceals  the  acid  nature  of  the  substance.  The  difficulty  could  be 
avoided  easily,  if  thiophene-a-carboxylic  acid  possessed  a  simple  name.  It  would  be 
entirely  in  keeping  with  both  its  chemical  and  physical  properties  to  assign  it  a  name 
similar  to  benzoic  acid.  Inasmuch  as  the  grouping  "thenoyl,"  C4H8S — CO —  is  in  com- 
mon usage  already,  the  name  thenoic  acid  is  suggested,  The  prefix  "then"  corresponds  to 
"benz,"  andjustasC6H6— CONHOH  is  benzhydroxamic  acid,  so  C4H3S— CONHOH  is 
a-thenhydroxamic  acid. 

»  Pickard  and  Neville,  /.  Chem.  Soc.,  79,  847  (1901). 

24  Rimini,  Gazz.  chim.  itaL,  [2]  31,  90  (1901). 

S5  Oliveri-Mandala,   /.    Chem.    Soc.,   100,  916    (1905);    88,    428    (1911);    Atti. 
accad.  Lincei,   [5]    14,  ii,  162  (1905). 

»  Douglas,  Ber.,  25,  1312  (1892). 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2431 

study  the  chemical  behavior  of  pyromucyl-,  and  of  thenhydroxamic  acids, 
since  they  are  typical  members  of  a  legion  of  unstudied  heterocylic  com- 
pounds. 

Pickard  and  Neville23  stated  "an  aqueous  solution  of  the  sodium  salt" 
of  the  benzoyl  ester  of  pyromucyl-hydroxamic  acid,  C4H3O — CO — NNa — - 
O — COCeHs,  "when  boiled  with  water  evolves  carbon  dioxide  and  an  oil 
(containing  nitrogen)  is  obtained  when  the  solution  is  evaporated.  The 
oil  is  presumably  difurfuran-carbamide,  but  decomposes  completely  when 
hydrolyzed.  No  better  success  was  obtained  on  attempting  to  prepare  the 
carbamates  by  boiling  the  sodium  salt  with  alcohols." 

A  year  later,  Curtius  and  .Leimbach27  tried  to  isolate  sym.  difuryl  urea, 
CO(NH— C4H3O)2,  from  the  azide,  C4H3O— CO— N3,  and  met  with  only 
partial  success.  Crystals  melting  at  229°,  and  at  220°  were  obtained. 
The  former  was  found  to  contain  12.01%  of  nitrogen,  the  latter  12.13%. 
The  calculated  percentage  for  difuryl  urea  is  14.56%. 

In  the  present  study,  it  was  found  that  when  the  potassium  salt,C4H3O — 
CO — NK — OCOC6H5,  was  warmed  gently  in  water  solution,  and  cooled 
at  the  first  evidence  of  precipitation,  the  precipitate  formed  was  the  free 
benzoyl  ester,  C4H3O— CO— NH— OCOC6H5.  This  compound  is  pro- 
duced by  hydrolysis,  not  by  rearrangement.  When  this  same  filtrate  was 
heated  to  boiling,  much  carbon  dioxide  was  evolved,  and  a  red  resinous 
mass  precipitated;  after  purification,  it  melted  at  about  210°.  This 
material  is  similar  to  the  product  found  by  Curtius  and  Leimbach. 

Thenhydroxamic  acid  derivatives  were  observed  to  undergo  a  slight 
hydrolysis  also,  but  rearrangement  to  form  sym.  di-thienyl  urea  was  a 
simple  matter.  Curtius  and  Thyssen28  obtained  this  same  urea  from  the 
azide,  C4H3S— CO — N3.  The  properties  of  their  compound  check  with 
those  of  ours  in  all  respects.  The  normal  reaction,  then,  is  as  follows, 

2C4H3SCONKOCOC6H6+H2O  — >   CO(NH— C4H3S)2+CO2+2C6H5— COOK. 

This  behavior  is  entirely  analogous  to  that  of  the  salts  of  dibenzhydrox* 
amic  acid. 

It  will  be  noticed  that  the  benzoyl  ester  of  thenhydroxamic  acid  is 
isomeric  with  the  thenoyl  ester  of  benzhydroxamic  acid.  The  latter  com- 
pound was  prepared.,  so  that  comparative  properties  of  the  two  might  be 
observed.  Melting  points  of  the  pure  substance,  and  the  temperatures  at 
which  the  potassium  and  the  silver  salts  decomposed  were  for  the  former 
144°,  125°  and  168°;  for  the  latter,  133°,  135°  and  165°:  respectively. 
The  ease  of  rearrangement  of  the  potassium  or  the  sodium  salts  in  aqueous 
solution  was  nearly  identical.  Too  much  stress  should  not  be  laid  upon  the 
temperature  of  decomposition  of  the  solid  salts.  The  figures  are  of  im- 
portance, but  the  method  of  applying  heat  to  determine  the  temperature 

27  Curtius  and  Leimbach,  J.  prakt.  Chem.,  [2]  65,  37  (1902). 

28  Curtius  and  Thyssen,  ibid.,  [2]  65,  17  (1902). 


2432  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

of  decomposition  influences  them  very  much.  For  example,  when  the 
potassium  salt  of  the  latter  compound  is  heated  slowly  there  is  no  visible 
action  until  about -160°.  However,  if  the  tube  containing  the  salt  is 
suddenly  thrust  in  a  bath  at  135°,  there  is  violent  decomposition.  With 
most  of  the  salts,  however,  there  is  a  fairly  definite  temperature  at  which 
they  explode  when  heat  is  applied  gradually. 

The  physical  and  some  of  the  chemical  properties  of  thiophene  com- 
pounds are  very  similar  to  those  of  corresponding  benzene  compounds. 
Thenhydroxamic  acid  is  no  exception.  It  melts  at  124°,  while  benzhy- 
droxamic  acid  also  melts  at  124°.  It  is  of  interest  to  note  that  di-thenhy- 
droxamic  acid  melts  much  lower  than  di-benzhy droxamic  acid .  The  former 
was  found  to  exist  in  two  modifications,  one  melting  at  105-107°,  and  the 
other  at  83-86 °.  Dibenzhydroxamic  acid  is  reported  by  Lessen80  to  melt  at 
145°.  Both  of  these  heterocyclic  hydroxamic  acids  resemble  benzhydrox- 
amic  acid  in  that  they  form  an  acid  ammonium  salt,31  (R — CO — NH — O)2- 
H.NH4,  which  is  difficultly  soluble  in  water. 

Experimental  Part. 

1.  Preparation  of  Diphenyl-acethydraxamic  acid, 
(G»H6)jCH.CO.NHOH. 

First  Method.  From  Ethyl  Diphenyl-acetate. — Thirty  g.  of  ethyl  diphenyl-acetate 
was  dissolved  in  180  cc.  of  methanol  which  contained  a  little  more  than  the  calculated 
amount  of  free  hydroxylamine.  The  hydroxylamine  was  liberated  from  15  g.  of  its 
hydrochloride  by  a  solution  of  sodium  methylate,  wh;ch  -contained  4.8  g.  of  sodium. 
To  this  mixture  a  solution  of  3.3  g.  of  sodium  in  60  cc.  of  methanol  was  added.  After 
10  hours,  the  mixture  was  diluted  with  one  liter  of  water,  and  the  hydroxamic  acid 
was  precipitated  with  dil.  sulfuric  acid.  The  filtrate,  separated  from  this  precipitate, 
contained  a  little  diphenyl-acethy droxamic  acid.  By  the  addition  of  a  solution  of 
copper  acetate  to  this  filtrate.  4  g.  of  the  green  copper  salt  was  obtained. 

A  solution  of  sodium  carbonate  was  used  to  purify  the  crude  diphenyl-acethy  drox- 
amic acid,  since  it  was  found  to  dissolve  all  of  the  diphenyl-acetic  acid  present,  but  none 
of  the  hydroxamic  acid.  The  insoluble  part  was  removed  and  washed  several  times  with 
water,  and  when  dry»  weighed  35  g.  The  crude  material  melted  between  145°  and  168° 
Recrystallization  from  ethyl  acetate  formed  needle-shaped  crystals  melting  at  172°. 

Diphenyl-acethydroxamic  acid  is  soluble  in  acetone,  in  ethyl  acetate,  in  ethyl  alco- 
hol, and  in  a  warm  solution  of  sodium  hydroxide.  It  is  insoluble  in  water,  in  a  solution 
of  sodium  carbonate  (hot),  in  ligroin,  in  benzene,  in  ether,  or  in  chloroform.  An  alco- 
holic solution  yields  the  characteristic  red  color  with  ferric  chloride. 

Analyses.  Subs.,  0.1470,  0.1589:  CO,,  0.3962,  0.4321:  H2O,  0.0767,  0.0852. 
Calc.  for  Ci4Hi8O2N:  C,  73.98;  H,  5.77.  Found:  C,  73.53,  7418;  H,  5.84,  6.00. 

Subs.,  0.3042:  N,  16.8  cc.  (24°  and  743.3  mm.  (17.5°))  30%  KOH  sol.  used.  Calc. 
N,  6.17.  Found:  6.08. 

Diphenyl-acethydroxamic  acid  could  not  be  prepared  in  quantity  by  the  action 
of  ethyl  diphenyl-acetate  upon  free  hydroxylamine.  Enough  was  formed  to  give  a 
purple  coloration  with  ferric  chloride,  but  in  order  to  obtain  a  satisfactory  yield,  one 
mol.  of  sodium  methylate  (or  its  equivalent)  seemed  essential. 

80  Lossen,  Ann.,  161,  347  (1872). 

31  Lossen,  ibid.,  281,  172  (1894). 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2433 

Second  Method.  From  Diphenyl-acetyl  Chloride. — Diphenyl-acethydroxamic  acid 
was  also  prepared  from  diphenyl-acetyl  chloride,  although  the  method  was  less  satis- 
factory because  of  side  reactions.  A  solution  of  1.9  g.  of  hydroxylammonium.  chloride 
in  a  small  amount  of  water,  was  mixed  with  a  solution  of  2.8  g.  of  sodium  carbonate. 
After  carbon  dioxide  had  escaped,  6  g.  of  diphenyl-acetyl  chloride  crystals  was  added 
and  the  mixture  was  shaken  vigorously.  When  the  reaction  had  apparently  ceased, 
the  product  was  warmed  to  60°,  then  filtered  to  collect  the  solid.  When  the  filtrate 
was  acidified,  half  a  gram  of  diphenyl-acetic  acid  (m.  p.  145°)  precipitated. 

The  residue  obtained  by  filtration  (5  g.)  gave  a  double  melting  point,  155-160°, 
and  215-230°.  Recrystallization  from  ethyl  acetate  led  to  the  separation  of  diphenyl- 
acethydroxamic  acid  (m.  p.  172°),  and  sym.  bi-diphenylmethyl  urea  (m.  p.  269-270°), 
CO(NH.CH(C6H6)2)2,  which  will  be  described  later.  Yield  of  the  hydroxamic  acid, 
2  to  3  g. 

Third  Method.    From  Diphenyl  Ketene. — Diphenyl  ketene  was  prepared  by  Schroe- 
(C6H5)2C=C=0+NH2OH  — >    (C6H6)2C— C=O 

I       I 
H      NHOH 

ter's  method.82  Azibenzil,  formed  by  the  oxidation  of  29  g.  of  benzil  hydrazone  dissolved 
in  120  cc.  of  dry  benzene,  was  warmed  to  60°  in  a  current  of  dry  carbon  dioxide  for 
about  3  hours,  until  evolution  of  nitrogen  had  ceased. 

Two  g.  of  freshly  distilled  hydroxylamine  was  suspended  in  a  mixture  of  50  cc.  of 
absolute  ether  and  20  cc.  of  ethyl  acetate,  which  had  been  carefully  purified  to  remove 
traces  of  alcohol,  water,  or  acetic  acid.  To  this  mixture,  100  cc.  of  the  benzene  solution 
of  diphenyl  ketene  was  added,  while  ah*  was  excluded  carefully  by  maintaining  an 
atmosphere  of  dry  hydrogen  gas.33  Ether  was  employed  to  increase  the  solubility  of 
hydroxylamine,  which  is  insoluble  in  benzene.  A  better  yield  would  be  obtained,  no 
doubt,  if  an  ether  solution  of  diphenyl  l^etene  were  used,  but  in  this  preparation  the 
yield  was  of  secondary  interest. 

After  the  mixture  had  been  shaken  thoroughly,  the  product  gradually  darkened. 
From  time  to  time,  the  stopper  of  the  flask  was  lifted  momentarily  to  release  the  pressure, 
probably  caused  by  the  decomposition  of  some  hydroxylamine.  After  two  hours, 
very  little  pressure  accumulated;  so  the  flask  was  left  overnight.  The  solvent  was 
then  distilled  at  the  temperature  of  a  water-bath  and  the  residue  was  poured  into  an 
Erlenmeyer  flask  to  crystallize.  The  crystals  secured  in  this  way  were  crystallized 
from  ethyl  acetate  and  petroleum  ether  Yield,  4  g.  After  one  recrystallization, 
the  melting  point  was  169-172°. 

To  establish  the  identity  of  this  compound  and  diphenyl-acethydroxamic  acid 
prepared  above,  the  benzoyl  esters  of  both  were  made  and  found  to  possess  identical 
properties.  Both  preparations  melted  at  140°.  (See  below.)  . ; 

Fourth  Method.  From  the  Copper  Salt. — Apparently,  there  are  two  forms  of  mono- 
phenyl-acethydroxamic  acid.  By  the  decomposition  of  the  copper  salt  with  hydrogen 
sulfide,  Thiele  and  Pickard9  obtained  a  compound  melting  at  121°.  Phenyl-acethy- 
droxamic  acid  which  melted  at  145°  was  prepared  by  Jones  by  the  interaction  of  free 
hydroxylamine  and  ethyl  phenyl -acetate.  It  was  thought  probable  that  a  second  form  of 
diphenyl-acethydroxamic  acid  might  be  obtained,  if  the  copper  salt  should  be  suspended 
in  alcohol  and  decomposed  by  hydrogen  sulfide,  but  such  was  not  found  to  be  the  case. 

Benzoyl  Ester:  (C6H5)2CH.CO.NHO— CO.C6H6.— Three  and  five-tenths  g.  of  di- 
phenyl-acethydroxamic acid  was  dissolved  in  a  warm  solution  of  potassium  hydroxide 

32  Schroeter,  Ber.,  42,  2345  (1909);  Staudinger,    Ref   21,  p.  144. 

33  C02  reacts  with  NH2OH. 


2434  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

just  sufficient  to  cause  the  solution  of  the  acid.  Benzoyl  chloride  (1.65  cc.)  was  added 
in  4  portions.  The  reaction  mixture  was  constantly  agitated,  while  a  stream  of  cold 
water  was  played  over  the  flask.  This  gave  6  g.  of  crude  dry  product.  Crystallization 
of  this  material  from  alcohol  yielded  plates  which  melted  at  139.5-141°.  Three  re 
crystallizations  caused  the  compound  to  have  a  sharp  melting  point,  140-140.5°.  This 
ester  is  soluble  :n  acetone,  in  ethyl  acetate,  in  chloroform  and  in  hot  alcohol;  slightly 
soluble  in  ether  and  m  benzene,  and  insoluble  in  water,  in  ligroin  and  in  a  cold  solution 
of  sodium  hydroxide.  When  the  solution  of  sodium  hydroxide  is  warmed,  rearrange- 
ment takes  place.  When  the  ester  was  heated  a  little  above  its  melting  point,  the  odor 
of  isocyanate  became  noticeable  at  once. 

Analysis.  Subs..  0.5417:  N,  20.6  cc.  (over  40%  KOH,  at  26°  and  740.1  mm.) 
Calc.  for  C;iH17O,N:N,  4.22.  Found:  4.13. 

Potassium  Salt.  (CeHs^CH.CO.NK.O.CO.CftHs.— First  Method.  Alcoholic  po- 
tassium hydroxide  was  prepared  of  such  a  strength  that  1  cc.  =  0.113  g.  of  KOH. 
One  cc.  of  this  reagent  was  added  to  a  solution  of  0.67  g.  of  the  benzoyl 
ester  in  a  mixture  of  15  cc.  of  absolute  alcohol  and  10  cc.  of  dry  ether,  previously  cooled 
to  — 15°.  There  was  no  precipitation  when  a  sample  of  the  solution  was  diluted  largely 
with  ether,  or  with  petroleum  ether.  Part  of  the  solution  was  treated  with  silver 
nitrate  to  form  the  silver  salt  (see  p.  2435).  The  rest  was  evaporated  in  vacua  over 
cone,  sulfuric  acid.  For  convenience,  the  residue  left  after  evaporation  of  the  solution 
will  be  called  "R." 

This  residue  (R)  was  shown  to  consist  of  a  mixture  of  the  desired  potassium  salt, 
together  with  diphenyl-methyl  isocyanate,  diphenyl-methyl  urethane,  and  potassium 
benzoate.  The  part  of  (R)  which  was  soluble  in  ether  was  extracted  and  half  of  this 
ether  solution  was  evaporated.  A  residue  remained  which  melted  at  90  °  to  100°.  Two 
recrystallizations  of  this  material  from  benzene  and  ligroin  resulted  in  the  isolation  of 
the  urethane,  (C«H6)2CH.NH.CO.OCjH»,  melting  at  124°.  The  properties  of  this 
compound  were  confirmed  by  its  preparation  from  diphenyl-acetamide,  (see  below). 

The  other  half  of  the  portion  soluble  in  ether  was  shown  to  contain  the  isocyanate, 
(CeH6)2CH.NCO,  since  an  ether  solution  of  benzhydryl-amine  added  to  Ft,  caused  an 
immediate  precipitate  of  the  urea,  m.  p.  268-270°,  according  to  the  equation, 

(C6H6)2CH.N:C:O+(C«H6)2CH.NH2  >   CO(NH.CH(C«H6)2)2. 

Benzhydryl-amine  is  without  action  upon  an  ether  solution  of  the  urethane. 

The  residue  left  from  (R)  after  ether  extraction  was  also  divided  into  two  parts. 
One  part  was  analyzed  and  was  found  to  contain  a  much  greater  percentage  of  potas- 
sium than  that  calculated  for  the  potassium  salt,  (C6H8)2CH.CO.NK.O.CO.C«H|. 

Analysis.    Subs.,    0.1385:    KzSO*,    0.0441.     Calc.     for    C2iH,«O»NK : K,    10.58. 
Found:  14.30. 
This  would  indicate  the  presence  of  potassium  benzoate  as  an  impurity. 

The  other  part  dissolved  in  water  to  give  a  clear  solution.  A  portion  of  the  solu- 
tion was  boiled;  this  caused  an  immediate  precipitation  of  sym.  bi-diphenylmethyl  urea, 
which  confirms  the  presence  of  some  potassium  salt  of  the  benzoyl  ester.  The  re- 
mainder of  the  solution,  acidified  with  dil.  hydrochloric  acid,  gave  a  precipitate  which, 
by  fractional  crystallization  from  alcohol,  was  resolved  into  the  original  benzoyl  ester 
of  diphenyl-acethydroxamic  acid,  m.  p.  140°,  and  benzoic  acid,  m.  p.  121°. 

Second  Method.  A  solution  of  potassium  ethylate  prepared  from  metallic  po- 
tassium instead  of  potassium  hydroxide  gave  no  different  results. 

An  interesting  observation  was  made  concerning  the  extreme  solubility  of  the 
potassium  salt.  When  0.33  g.  of  the  benzoyl  ester  was  suspended  in  a  cold  mixture 
of  3  cc.  of  alcohol,  and  6  cc.  of  ether,  the  undissolved  ester  went  into  solution  when 
alcoholic  potash  was  added. 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2435 

Third  Method.  About  0.36  g.  of  silver  salt,  (CeHs^CH.CO.NAg.O.CO.CeHa 
(see  preparation,  below)  suspended  in  4  cc.  of  ice-water,  was  treated  with  0.12  g.  of 
potassium  bromide,  dissolved  in  a  little  water.  The  mixture  was  stirred  frequently. 
After  an  hour,  the  precipitate  had  assumed  the  yellow  color  of  silver  bromide.  Ample 
roof  of  metathesis  was  furnished  when  a  little  of  the  solution  was  filtered,  and  heated. 
A  heavy  crystalline  precipitate  of  sym.  bi-diphenylmethyl  urea  (m.  p.  268-270°) 
separated.  There  appears  to  be  no  record  of  the  use  of  silver  salts  in  the  preparation 
of  alkali  salts  of  hydroxamic  acid. 

The  reaction  mixture  was  kept  at  0°  overnight.  Little,  if  any,  decomposition 
occurred.  One-third  of  the  solution,  after  filtration,  was  acidified.  The  benzoyl  ester 
precipitated  in  quantity.  When  a  second  portion  of  this  solution  was  allowed  to  stand 
at  room  temperature,  a  gradual  precipitation  of  the  urea  took  place. 

A  portion  of  the  solution  containing  the  potassium  salt  was  treated  with  silver 
nitrate,  copper  acetate,  and  cobalt  nitrate  solutions.  The  colors  of  the  three  precipi- 
tates were  white,  light  green,  and  light  pink  respectively.  These  salts  were  not  studied 
further. 

Sodium  Salt.  (CeHs^CH.CO.N.Na.O.CO.CeHs. — A  convenient  solution  of  sodium 
ethylate  to  employ  is  one  in  which  1  cc.  =c=  0.023  g.  of  sodium.  To  a  solution  of  0.3 
g.  of  benzoyl  ester  in  4  cc.  of  absolute  alcohol  and  15  cc.  of  ether,  0.9  cc.  of  the  sodium 
ethylate  solution  was  added.  (The  ester  was  in  slight  excess.)  Just  as  with  the 
potassium  salt,  here,  also,  no  precipitate  could  be  obtained.  One  portion  of  this  solution 
was  saved  for  the  preparation  of  the  silver  salt,  (see  below)  while  a  second  pbrtion 
of  the  solution  was  evaporated  rapidly,  and  the  residue  extracted  with  water.  Fil- 
tration from  the  insoluble  matter  left  a  clear  solution  that  soon  became  turbid.  A 
precipitate  of  the  urea  derivative  was  formed  by  boiling  the  solution. 

The  remainder  of  the  ether-alcohol  solution  was  evaporated  in  vacua  over  cone, 
sulfuric  acid.  Ether  caused  the  extraction  of  a  large  amount  of  the  urethane,  m.  p., 
123-124°.  The  portion  insoluble  in  ether  was  shown  by  analysis  to  be  chiefly  sodium 
benzoate. 

Analysis.  Subs.,  0.0558:  Na2SO4,  0.0251.  Calc.  for  C^HieOsNNa:  Na,  6.51. 
Calc.  for  C6HB.COONa:  Na,  15.97.  Found:  14.56. 

Silver  Salt.  (CeH^CH.CO.NAg.O.CO.CeHs. — First  Method:  from  the  potassium 
salt.  The  ether-alcohol  solution  of  the  potassium  salt  (see  p.  2434)  was  treated  with 
an  aqueous  solution  of  silver  nitrate.  The  ether  layer  instantly  assumed  a  deep  yellow 
color,  but  remained  clear.  When  this  solution  was  shaken,  a  pure  white  precipitate 
of  the  silver  salt  formed,  and  the  yellow  color  of  the  ether  layer  disappeared  simul- 
taneously. 

Analysis.  Subs.,  0.1164:  Ag,  0.0285.  Calc.  for  C2iHi6O3NAg:  Ag,  24.62.  Found: 
24.49. 

A  little  of  the  white  salt,  suspended  in  ether,  did  not  cause  the  ether  to  assume  a 
yellow  color,  even  when  alcohol  was  added.  Here,  again,  as  with  the  sodium  or  the 
potassium  salt,  there  is  evidence  of  the  existence  of  two  modifications,  one  of  which 
is  soluble  in  ether  and  alcohol,  and  the  other  insoluble.  Gradual  rearrangement  occurred 
when  the  salt  was  heated  gently;  the  odor  of  isocyanate  was  very  marked.  In  a  small 
tube  the  salt  decomposed  with  a  puff  at  about  145°. 

Second  Method:  from  the  sodium  salt.  A  similar  procedure  was  followed  with 
an  ether-alcohol  solution  of  the  sodium  salt  (see  above).  In  this  case,  the  ether 
layer  became  yellow  in  color,  and  the  precipitate  which  formed  was  yellow  as  well. 
The  color  of  the  salt  gradually  changed  to  pure  white,  and,  in  so  doing,  formed  needle- 
shaped  crystals.  This  change  of  color  was  hastened  by  scratching  the  precipitate 
with  a  glass  rod.  That  the  color  change  commenced  at  the  surface  was  proved;  for 


2436  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

yellow  clumps  that  had  apparently  turned  white,  were  found  still  to  be  yellow  at  the 
center.  This  material,  when  heated  on  a  spatula,  decomposed  with  a  puff  to  form  the 
isocyanate  and  a  residue  of  metallic  silver  was  left  after  ignition. 

Di-acetyl  Ester,  (C8H5)1CH.CO.N(CO.CH,).O.CO.CH,.— Apparently,  the  normal 
reaction  of  acetic  anhydride  and  diphenyl-acethydroxamic  acid  leads  to  the  formation 
of  the  di-acetyl  ester,  a  trihydroxamic  acid,  instead  of  the  mono-acetyl  ester,  even 
when  half  a  mol.  of  acetic  anhydride  is  used.  In  this  case,  a  mixture  of  mono-  and  di- 
acetyl  derivatives  is  obtained.  By  recrystallization  from  alcohol,  the  mixture  was 
separated  only  with  the  greatest  difficulty. 

To  prepare  the  di-acetyl  ester,  diphenyl-acethydroxamic  acid  (3  g.)  was  dissolved 
in  a  large  excess  of  acetic  anhydride  (10  cc.).  This  solution  was  kept  warm  for  2  hours, 
and  the  excess  of  acetic  anhydride  was  then  evaporated  in  a  vacuum  desiccator  con- 
taining powdered  alkali.  The  solid  ester,  after  recrystallization  from  alcohol,  melted 
at  95.5-97.5°.  It  is  soluble  in  hot  alcohol,  in  ethyl  acetate,  in  chloroform,  in  acetone 
and  in  benzene.  It  is  but  slightly  soluble  in  ether,  and  is  insoluble  in  water,  in  ligroin, 
or  in  a  solution  of  sodium  hydroxide. 

Analysis.  Subs.,  0.5008:  N,  19.8  cc.  (over  40<?f  KOH  at  25°  and  743.8  mm. 
(26°))  Calc.  for  CiSH17O4N:  N,  4.50.  Found:  4.34 

Two  g.  of  the  di-acetyl  ester  was  distilled  in  a  small  flask  heated  by  a  metal  bath. 
A  liquid  that  weighed  0.45  g.  was  collected  when  the  temperature  of  the  bath  rose  to 
between  200°  and  300°.  This  liquid  all  redistilled  between  120  °  and  138° ;  this  fraction 
consisted  chiefly  of  acetic  anhydride.  When  the  residue  in  the  flask  was  heated  with 
a  free  flame,  a  liquid  distilled  at  about  300°  and  left  resinous  materials  in  the  flask. 
When  the  distillate  was  treated  with  an  ether  solution  of  benzhydryl-amine  to  detect 
any  diphenylmethyl  isocyanate  and  then  diluted  with  an  equal  quantity  of  petroleum 
ether,  a  tardy  precipitate  resulted;  m.  p.  136-137°.  This  was  identified  as  benzhydryl- 
amine  acetate;  no  sym.  bi-diphenylmethyl  urea  could  be  found. 

Benzhydryl-amine  Acetate,  (C^Hs^CH.NHaO.COCHs. — A  sample  of  benzhydryl- 
amine  acetate  was  prepared  by  mixing  an  ether  solution  of  benzhydryl-amJne  with 
glacial  acetic  acid.  Wrhite  crystalline  plates  separated,  which  melted  at  138°.  The 
salt  dissolved  readily  in  water. 

Mono-acetyl  Ester,  (C«H6)2CH.CO.NH — O— CO.CH8.— In  order  to  avoid  the  for- 
mation of  the  di-acetyl  ester,  precautions  had  to  be  tak^ri  to  destroy  the  acetic  anhydride 
as  soon  as  the  reaction  mixture  showed  no  mono-hy  uroxamic  acid.  Ferric  chloride  was 
used  as  an  indicator.  Three  g.  of  diphenyl-acethydroxamic  acid  was  dissolved  rapidly 
in  an  excess  of  warm  acetic  anhydride  (10  cc.),  and,  after  about  30  seconds,  the  re- 
action was  stopped  by  the  addition  of  50  cc.  of  cold  water.  A  white  precipitate,  chiefly 
the  mono-acetyl  ester,  resulted.  Two  recrystallizations  gave  crystalline  plates  of 
pure  substance  melting  at  113-113.5°. 

The  acetyl  ester  dissolves  in  acetone,  in  chloroform,  in  ethyl  acetate  in  benzene 
and  in  alcohol.  It  is  insoluble  in  a  cold  solution  of  sodium  hydroxide  and  in  ligroin, 
and  only  slightly  soluble  in  ether.  When  the  solution  of  sodium  hydroxide  is  warmed, 
rearrangement  takes  place. 

Analysis.  Subs.,  0.3046:  N,  14.1  cc.  (over  40%  KOH  at  23.5°  and  738.8  mm. 
(19°)).  Calc.  for  Ci«HuO«N : N,  5.20.  Found:  5.09 

Potassium  Salt. — (CeH6)2CH.CO.NK.O.CO.CH3. — One-third  of  a  gram  of  acetyl 
ester  dissolved  quite  readily  in  5  cc.  of  cold  alcohol.  The  solution  was  diluted  with  10 
cc.  of  ether  and  was  then  chilled  to  — 10°  by  means  of  a  freezing  mixture  of  ice  and  cone, 
sulfuric  acid.  To  this  solution,  0.6  cc.  of  alcoholic  potash  solution  (see  p.  2434) 
was  added.  Here  again,  no  precipitate  formed,  even  when  an  excess  of  ether  was 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2437 

added.     Part  of  the  liquid  was  evaporated;  the  residue  was  extracted  with  ether,  dried 
and  analyzed. 

Analysis.  Subs.,  0.0929 :  K2SO4,  0.0293.  Calc.  for  CieHuOsNK:  K,  12.72.  Found: 
14.15.  •- 

This  high  result  is  explained  by  the  presence  of  potassium  acetate,  a  decom- 
position product. 

The  remainder  of  the  solution,  which  still  contained  the  potassium  salt,  was  diluted 
with  10  cc.  of  petroleum  ether.  There  was  no  precipitate.  If  it  was  shaken  with  a 
dil.  solution  of  silver  nitrate  in  water,  a  white  silver  salt  was  obtained  (see  below). 

Sodium  Salt — About  0.3  g.  of  the  acetyl  ester  was  dissolved  in  2  to  3  cc.  of  absolute 
alcohol,  and  diluted  to  15  cc.  with  ether.  This  solution,  cooled  with  ice,  was  treated 
with  Q.8  cc.  of  sodium  ethylate  solution  (see  p.  2435).  There  was  a  tardy  precipi- 
tation that  gradually  became  quite  heavy.  The  addition  of  ether  hastened  its  for- 
mation This  material,  collected  and  washed  with  ether,  was  dried  and  analyzed. 
Its  sodium  content  was  found  to  be  midway  between  that  required  for  (CeHo^CH.CO.- 
NNa.O.COCH,  and  that  for  sodium  acetate. 

Analysis.  Subs.,  0.0634:  Na2SO4,  0.0346.  Calc.  for  deHuOjNNa:  Na,  7.90. 
Calc.  for  CH3.COONa:  Na,  28.05.  Found:  17.67. 

Silver  Salt. — The  ether-alcohol  solution  of  the  potassium  salt,  when  mixed  with 
aqueous  silver  nitrate,  formed  a  pure  white  precipitate.  It  was  found  best  not  to  wash 
the  salt  with  alcohol,  since  that  frequently  caused  it  to  turn  dark.  The  white  pre- 
cipitate was  washed  carefully  with  water,  dried,  and  analyzed.  When  it  was  heated 
in  a  small  tube,  it  decomposed  between  103°  and  110°.  The  isocyanate,  recognized 
by  its  characteristic  odor,  distilled. 

Analysis.  Subs.,  0.0738:  Ag,  0.0213.  Calc.  for  CieHuOsNAg:  Ag,  28.69.  Found: 
28.86. 

In  order  to  establish  the  identity  of  the  products  of  rearrangement  isolated  in  these 
reactions,  they  were  prepared  in  a  different  manner.  Some  of  them  represent  new  com- 
pounds, not  previously  described. 

Diphenylmethyl  Urethane,  (C6H5)2CH.NH.COOC2H5.— A  method,  similar  to  that 
developed  by  Stieglitz  and  his  students,34  was  employed  successfully  in  the  preparation 
of  this  ure thane.  A  solution  of  sodium  ethylate  was  made  by  the  action  of  3.42  g. 
of  sodium  upon  160  cc.  of  alcohol.  Nine  g.  of  diphenyl-acetamide  was  suspended  in  it, 
and  caused  to  dissolve  by  the  rapid  addition  of  4.1  cc.  of  bromine.  Without  filtration 
to  remove  sodium  bromide,  the  neutral  mixture  was  boiled  for  10  minutes,  after  which 
the  alcohol  was  distilled.  The  urethane  was  precipitated  by  the  addition  of  an  excess 
of  water.  Yield,  8  g.  Nothing  except  sodium  bromide  was  found  in  the  filtrate.  The 
precipitate  was  extracted  with  50  cc.  of  hot  benzene.  One  g.  of  material,  later  proved 
to  be  sym.  bi-diphenylmethyl  urea,  was  insoluble.  When  the  benzene  became  cool, 
1.8  g.  of  unchanged  amide  (m.  p.  161°)  precipitated.  The  benzene  filtrate  contained 
nearly  pure  diphenylmethyl  urethane.  After  evaporation  of  the  solvent,  the  residue 
was  pressed  on  a  clay  plate.  Yield,  4.2  g.  It  may  be  recrystallized  from  a  mixture  of 
benzene  and  ligroin,  or  of  alcohol  and  water;  m.  p.  122-123°.  It  is  soluble  in  alcohol, 
in  chloroform,  in  acetone,  in  ethyl  acetate,  and  in  benzene,  but  insoluble  in  water  and 
in  ligroin. 

Analysis.     Subs.,  0.4130:  N,  20.69  cc.  (over  40%  KOH  at  20°  and  763.9  mm. 
(16°)).     Calc.  for  CieHnOsN:  N,  5.49.     Found:  5.64. 
Diphenylmethyl   urea    chloride,   (C6H5)2CH.NH.CO.C1.— Two  g.    of  the  urethane 

34  Jeffreys,  Ber.,  30,  898  (1897);  Am.  Chem.  J.,  22,  27  (1899);  Folin,  Am.  Chem. 
J.,  19,  324  (1897). 


2438  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

and  1.63  g.  of  phosphorus  pentachloride  were  dissolved  in  10  to  15  cc.  of  dry  chloroform. 
This  mixture  was  warmed,  and  a  current  of  dry  hydrogen  chloride  was  bubbled  through 
the  solution.  This  served  to  expel  phosphorus  oxychloride  and  also  to  prevent  the 
decomposition  of  the  urea  chloride  which  would  yield  the  more  volatile  isocyanate. 
Chloroform  was  added  twice  as  the  solution  evaporated.  Finally,  when  the  solvent 
was  nearly  exhausted,  petroleum  ether  was  added,  and  the  entire  solution  was  poured 
through  a  filter.  A  solid  mixed  with  oil  resulted  when  the  filtrate  was  evaporated. 

Diphenylmethyl  Isocyanate,  (C6H6)iCH.NCO. — The  crude  urea  chloride  was 
extracted  with  benzene,  and  the  solution  filtered.  Some  calcium  oxide  was  placed  in 
the  flask,  and  the  mixture  was  left  in  the  stoppered  flask  for  3  hours.  This  solution 
contained  the  isocyanate  (see  below).  After  filtration,  it  was  not  purified  further,  but 
was  treated  at  once  with  benzhydryl-amine  to  form  the  urea 

Benzhydryl-amine,  (C*H5)2CH.NHj. — This  compound  wasp  repared  by  reducing 
benzophenone  oxime  with  metallic  sodium  and  alcohol.  It  has  been  prepared  from 
benzophenone  oxime  by  Goldschmidt,34  who  employed  sodium  amalgam,  and  also 
by  Michaelis36  from-benzophenone-phenylhydrazone  with  metallic  sodium  and  alcohol. 

Five  g.  of  dry  benzophenone  oxime  was  suspended  in  50  cc.  of  absolute  alcohol.  The 
mixture  was  poured  through  a  reflux  condenser  upon  a  piece  of  sodium  which  weighed 
12  g.  The  oxime  dissolved  at  once,  and  enough  heat  was  generated  to  melt  the  sodium. 
A  little  alcohol  was  introduced  from  time  to  time.  After  40  minutes,  when  all  the  sodium 
had  dissolved,  most  of  the  alcohol  was  recovered  by  distillation,  and  water  was  added 
to  the  residue.  After  partial  neutralization  of  the  alkaline  solution,  benzhydryl-amine 
was  extracted  by  means  of  ether,  and  the  ether  solution  was  dried  over  potassium  hy- 
droxide. To  precipitate  benzhydryl-amine  hydrochloride,  it  was  only  necessary  to 
add  cone,  hydrochloric  acid  to  the  ether  solution.  Between  5.5  and  6  g.  of  the  salt 
was  collected. 

Sym.  bi-diphenyhnethyl  Urea,  CO(NH.CH(C«H6)j)i. — The  benzene  solution  of  the 
isocyanate  (see  above)  was  treated  with  an  ether  solution  of  benzhydryl-amine. 
There  was  a  tardy  precipitation  of  solid  which  was  collected  after  a  few  hours  and  shown 
to  consist  of  a  mixture  of  benzhydryl-amine  hydrochloride,  and  the  urea.  The  former, 
produced  because  of  some  unchanged  urea  chloride,  was  soluble  in  very  dilute  hydro- 
chloric acid;  it  melted  at  276-280°.  The  portion  insoluble  in  the  acid  melted  at  266°. 
It  was  rather  soluble  in  hot  acetone  and  in  hot  ethyl  acetate.  Recrystallization 
from  either  of  these  solvents  produced  fine  needle-shaped  crystals  of  the  urea  which 
melted  at  269.5-270°. 

Analysis.  Subs.,  0.3246:  N,  19.90  cc.  (20°  and  763.9  mm.  (16°)).  Calc.  for 
Ci7H24ONj:  N,  7.14.  Found:  7.07. 

2.     Triphenyl-acethydroxamic  Acid. 

(C6H6)SC.CO.NHOH. 

Triphenyl-acetyl  chloride,  (C6H5)jC.COCl.— Schmidlin  and  Hodgson36  prepared 
triphenyl-acetyl  chloride  from  triphenyl-acetic  acid,  acetyl  chloride  and  phosphorus 
pentachloride.  In  the  same  year  Bistrzycki  and  Land  twig37  described  a  method  of 
preparation  in  which  phosphorus  oxychloride  was  used  as  a  solvent,  instead  of  acetyl 
chloride. 

It  may  be  prepared  much  more  simply  with  thionyl  chloride  as  the  chlorinating 
agent.  Three  g.  of  triphenylacetic  acid  and  10  cc.  of  thionyl  chloride  were  placed 

34  Goldschmidt,  Ber.,  19,  3233  (1886). 

35  Michaelis,  ibid.,  26,  2168  (1893). 

36  Schmidlin  and  Hodgson,  ibid.,  41,  438  (1908). 

37  Bistrzycki  and  Landtwig,  ibid.,  41,  687  (1908). 


RE  ARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2439 

in  a  small  flask  equipped  with  an  air  condenser,  and  gently  warmed  until  solution  was 
complete.  The  liquid  was  boiled  for  about  5  minutes  after  gas  evolution  (sulfur  dioxide 
and  hydrogen  chloride)  had  ceased.  Then,  it  was  cooled  and  poured  upon  crushed 
ice  to  decompose  any  excess  of  thionyl  chloride.  (If  larger  quantities  were  employed, 
it  would  be  better  of  course,  to  recover  the  thionyl  chloride  by  distillation.)  The  solid 
triphenylacetyl  chloride  was  filtered,  washed  with  a  little  cold  water,  pressed  upon  a 
porous  plate,  and  then  dried  in  a  vacuum  desiccator.  Without  further  treatment, 
the  material  obtained  was  pure  enough  for  most  purposes.  It  melted  at  127°.  The 
yield  was  practically  quantitative. 

Thionyl  chloride  readily  dissolved  both  triphenylacetyl  chloride,  and  ethyl 
triphenylacetate,  and  it  was  without  action  upon  either  one. 

Triphenylacethydroxamic  Acid. — Two  and  five-tenths  g.  of  triphenylacetyl  chloride 
was  dissolved  in  40  cc.  of  dry  benzene.  This  was  poured  into  a  flask  containing  2.5  g. 
of  free  hydroxylamine.  The  mixture  was  agitated  at  frequent  intervals  during  an 
hour,  and  then  was  put  aside  until  the  next  day.  Since  there  was  no  precipitation  of 
hydroxamic  acid,  the  benzene  layer  was  decanted  from  the  excess  of  hydroxylamine, 
placed  in  a  distilling  flask,  and  the  solvent  was  distilled.  An  oil  remained  which  crystal- 
lized readily  when  it  became  cool.  Petroleum  ether  caused  an  additional  precipitate. 
More  than  2  g.  of  crystals  was  obtained.  The  crude  substance  melted  at  172°. 

Triphenylacethydroxamic  acid  is  soluble  in  a  warm  solution  of  sodium  hydroxide, 
in  benzene,  in  acetone,  in  ethyl  acetate  and  in  alcohol.  It  is  insoluble  in  ligroin,  and 
in  water.  Recrystallization  from  ether  produced  a  pure  product  which  melted  at 
175-176°. 

An  alcoholic  solution,  treated  with  ferric  chloride,  gave  the  usual  red  color  reaction. 
Furthermore,  copper  acetate  formed  a  light  green  copper  salt. 

Analysis.  Subs.,  0.3858:  N,  16.14  cc.  (over  40%  KOH  at  21.8°  and  758.9  mm. 
(18°)).  Calc.  for  C2oH17O2N:  N,  4.62.  Found:  4.75. 

Attempts  to  prepare  triphenylacethydroxamic  acid  by  the  action  of  free  hydroxyl- 
amine upon  ethyl  triphenylacetate,  (CeHs^C.CO.OCaHs,  resulted  in  failure.  There 
was  no  action,  even  when  an  excess  of  sodium  ethylate  was  present.  In  all  cases  the 
ester  was  recovered  unchanged. 

When  triphenylacetyl  chloride  was  employed  with  a  mixture  of  hydroxylamine 
and  sodium  carbonate  in  water,  it  was  very  difficult  to  purify  the  triphenylacet- 
hydroxamic acid. 

Benzoyl  Ester,  (CeHs^C.CO.NH.O.CO.CeE^. — First  Method.  One-tenth  g.  of 
triphenylacethydroxamic  acid  was  fused  with  a  considerable  excess  of  benzoic  anhydride 
until  a  sample  gave  no  reaction  with  ferric  chloride.  The  excess  of  anhydride  was  then 
extracted  several  times  with  warm  ligroin  (50°).  An  oil  was  left  which  refused  to 
solidify  in  the  course  of  a  week.  It  was  extracted  with  a  very  dilute,  cold  solution  of 
sodium  hydroxide.  This  solution  was  filtered  and  acidified  immediately.  A  white 
solid  precipitated,  m.  p.  40-50°.  When  this  process  was  repeated  the  benzoyl  ester 
was  obtained  in  a  somewhat  purer  state.  It  melted  between  44°  and  47°  for  the  most 
part,  but  there  was  a  little  that  did  not  melt  until  the  temperature  reached  70°.  It 
is  highly  probable  that,  even  at  this  low  temperature,  the  ester  decomposed  to  a  slight 
extent  into  benzoic  acid  and  triphenylmethyl  isocyanate,  which  may  account  for  the 
anomolous  melting  point  (see  p.  2429). 

This  low-melting  ester  was  found  to  be  extremely  soluble  in  organic  solvents. 
From  benzene  solution,  petroleum  ether  precipitated  it  as  an  oil  which  could  not  be 
made  to  crystallize,  even  after  the  removal  of  the  solvent. 

By  careful  hydrolysis  with  alkalies,  it  was  possible  to  convert  part  of  the  ester 
into  triphenylacethydroxamic  acid.  The  greater  tendency  by  far,  however,  was 


2440  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

rearrangement  of  the  salt  in  solution,  not  to  form  the  urea  derivative,  as  would  be  antic- 
ipated, but  to  give  the  isocyanate,  (C«H6)jC.NCO. 

Second  Method.  Because  of  the  instability  of  the  sodium  salt  of  the  benzoyl 
ester  of  triphenylacethydroxatnic  acid,  this  method  (Schotten-Baumann  reaction) 
is  less  successful  than  the  first  method.  One  and  six-tenths  g.  of  triphenylacet- 
hydroxamic  acid  was  dissolved  in  15  cc.  of  water  that  contained  0.23  g.  of  sodium 
hydroxide.  The  solution  was  cooled  in  a  stream  of  tap  water,  and  0.6  cc.  of  benzoyl 
chloride  was  added  in  3  portions. 

No  attempt  was  made  to  purify  the  sticky  solid.  Instead,  it  was  washed  thoroughly 
with  water,  then  dried,  and  converted  into  its  salts. 

Potassium  Salt.  (CeHO.C.CO.NK.O.CO.CeHs.— The  crude  benzoyl  ester  was 
dissolved  in  1.5  cc.  of  absolute  alcohol.  This  solution  was  treated  with  a  solution  of 
potassium  hydroxide  (0.11  g.)  in  alcohol.  Since  20  cc.  of  ether  caused  no  precipitation 
of  salt,  a  solution  of  silver  nitrate  in  water  was  added.  This  gave  the  silver  salt. 

Silver  Salt.  (C«H6)iC.CO.NAg.O.CO.C«H6.— A  white  precipitate  formed,  which 
turned  canary-yellow  in  a  short  time.  It  was  filtered  and  washed  thoroughly  with  water, 
and  with  ether.  In  a  small  tube,  this  salt  became  gray  in  color  at  120°;  it  was  black 
at  160°;  and  at  195°  it  melted  with  much  decomposition. 

Analysis.  Subs.,  0. 1444 :  Ag,  0.0300.  Calc.  for  Ci7HjoOjNAg:  Ag,  20.98.  Found: 
2085. 

Acetyl  Ester,  (C6Hr)3C.CO.NH.O.CO.CH,. — A  large  excess  of  warm  acetic  anhy- 
dride (about  3  cc.)  was  used  to  dissolve  0.6  g.  of  triphenylacethydroxamic  acid.  In 
about  half  a  minute  a  test  with  ferric  chloride  showed  that  the  reaction  was  complete. 
In  order  to  stop  any  further  action  which  might  lead  to  the  formation  of  a  di-acetyl 
ester,  10  cc.  of  cold  water  was  added  to  decompose  any  unused  anhydride.  In  a  short 
time,  the  acetyl  ester  solidified  to  form  a  white  solid.  It  was  filtered  and  dried.  Very 
few  impurities  were  present  in  this  crude  material.  One  recrystallization  from  a  mix- 
ture of  2  cc.  of  benzene  and  10  cc.  of  ligroin  gave  a  pure  product  that  melted  at  133.5- 
134°.  The  ester  was  very  soluble  in  most  common  organic  solvents.  The  yield  was 
quantitative. 

Analysis.  Subs.,  0.2156:  N,  7.62  cc.  (20°  and  762.2  mm.).  Calc.  for  C**Hi,O|N: 
N,  4.06.  Found:  4.08. 

Potassium  Salt.  (C«H6)iC.CO.NK.O.CO.CH3.— When  0.38  g.  of  the  acetyl  ester 
was  dissolved  in  a  small  quantity  of  absolute  alcohol  and  neutralized  with  0.55  cc.  of 
alcoholic  caustic  potash  (0.062  g.  of  potassium  hydroxide),  a  little  ether  caused  the 
separation  of  a  gelatinous  precipitate,  which  was  collected  upon  a  filter.  The  material 
would  not  dissolve  to  give  a  clear  solution  in  cold  water.  It  was  evident  that  the 
unstable  potassium  salt  suffered  rearrangement  in  solution,  because  the  solution,  turbid 
at  first,  rapidly  became  white  and  opaque.  When  the  solution  was  boiled,  the  potassium 
salt  was  decomposed  completely;  triphenylmethyl  isocyanate  was  precipitated.  The 
dry  salt  decomposed  slightly  at  112°.  At  165°  there  was  a  vigorous  evolution  of  gas. 

Analyses.  Subs.,  0.0400,  0.1253:  K2SO4,  0.0080,  O.D252.  Calc.  for  C«H18  O3NK: 
K,  10.19.  Found:  8.98,  9.03. 

Sodium  Salt. — Sodium  ethylate  and  ether  did  not  cause  a  precipitate  when  added 
to  a  solution  of  the  acetyl  ester  in  alcohol.  Accordingly,  the  solution  was  treated  with 
an  aqueous  solution  of  silver  nitrate  to  form  the  silver  salt. 

Silver  Salt. — This  was  thrown  down  at  once  as  a  yellow  precipitate,  but  the  quantity 
was  insufficient  to  warrant  an  analysis.  When  heated  upon  a  spatula  it  decomposed 
at  a  fairly  high  temperature  and  left  a  residue  of  metallic  silver. 

Triphenylmethyl  Isocyanate,     (CeH^sC.NCO. — When  a  solution  of  the  potassium 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2441 

salt  of  the  acetyl  ester  of  triphenylacethydroxamic  acid  was  boiled  for  a  short  time 
with  water,  an  oil  was  formed.  In  the  course  of  a  few  hours  this  oil  solidified.  It 
was  collected,  and  washed  with  water.  The  isocyanate  was  very  soluble  in  organic 
solvents,  even  in  ligroin.  It  was  dissolved  in  petroleum  ether,  filtered  into  an  open 
dish,  and  most  of  the  solvent  evaporated  in  a  vacuum  desiccator.  White  crystals 
were  formed  in  this  manner,  m.  p.  85-87°. 

Analysis.  Subs.,  0.1518:  N,  6.72  cc.  (17°  and  757  mm.  (18°)).  Calc.  for  C22- 
H16ON:N,  4.91.  Found:  5.12. 

The  solubility  in  petroleum  ether,  and  the  low  melting  point  are  sufficient  evidence 
that  this  compound  could  not  be  sym.  bi-triphenylmethyl  urea,  CO(NH.C(C6H6)i)2. 
Although  E.  von  Meyer  and  P.  Fischer39  claim  to  have  prepared  this  urea,  none  of  its 
properties,  not  even  the  melting  point,  was  described.  It  can  be  predicted,  however, 
that  the  melting  point  is  very  high. 

In  order  to  prove  that  the  material  in  hand  was  the  isocyanate,  it  was  dissolved 
in  ether,  and  treated  with  the  calculated  quantity  of  aniline,  also  dissolved  in  ether. 
Upon  evaporation  of  the  ether,  a  white  solid  was  left  which  melted  sharply  at  242°. 
This  was  anticipated,  since  phenyl-triphenylmethyl  urea,  C«H5.NH — CO.NH.C(C6H6)i, 
which  has  been  prepared39  previously,  was  known  to  melt  at  that  temperature. 

3.  Pyromucyl-hydroxamic  Acid. 
I— CO.NHOH 


O 

The  procedure  described  by  Pickard  and  Neville24  for  the  preparation  of  pyromucyl- 
hydroxamic  acid  employed  ethyl  pyromucate  and  hydroxylamine  in  alcoholic  solution. 
It  was  purified  through  the  medium  of  the  insoluble  copper  salt.  Our  modification 
of  the  method  consists  in  the  addition  of  a  mol  of  sodium  ethylate,  and  the  direct  re- 
covery of  the  hydroxamic  acid  without  the  intermediate  formation  of  the  copper  salt. 

Thirty  g.  of  methyl  pyromucate  was  poured  into  150  cc.  of  a  methanol  solution  of 
free  hydroxylamine  which  had  been  liberated  from  19.5  g.  of  its  hydrochloride  by 
a  solution  of  sodium  methylate  containing  6.4  g.  sodium.  A  solution  of  5.4  g.  of  sodium 
in  70  cc.  of  methanol  was  then  added  to  the  mixture  and,  after  10  hours,  as  light  excess 
of  cone,  hydrochloric  acid  was  introduced.  Sodium  chloride  was  separated  and  the 
methanol  removed  by  distillation  in  vacuo.  An  oil  was  left  which  solidified  after  a 
few  hours  in  a  vacuum  desiccator.  One  crystallization  from  water  brought  the  melting 
point  to  119-122°.  Twenty-four  g.  of  this  material  was  obtained.  Three  g.  of  the 
copper  salt  was  precipitated  from  the  solvent  used  in  recrystallization. 

The  acid  is  soluble  in  alcohol,  in  ethyl  acetate,  and  in  water.  In  benzene,  in  chloro- 
form, in  carbon  disulfide,  in  ligroin,  and  in  ether  it  is  insoluble. 

Ammonium  Salt.  (CJlsO.CO.NH.O^H.NHi — Ammonium  hydroxide  caused 
the  precipitation  of  beautiful  crystalline  plates,  when  added  to  an  aqueous  solution  of 
pyromucyl-hydroxamic  acid.  (Cf.  p.  2444.)  This  precipitate  was  soluble  either  in 
an  excess  of  ammonium  hydroxide,  or  in  dilute  acid,  which  indicated  that  the  salt 
is  the  acid  salt  and  not  the  normal  salt.  In  the  former  case,  the  normal  salt  is  un- 
doubtedly obtained,  whereas  with  acids,  the  soluble  pyromucyl-hydroxamic  acid  is 
restored.  The  salt  melted  at  130-131°,  with  considerable  gas  evolution.  The  analysis 
gave  the  same  values  whether  the  salt  was  prepared  in  this  manner,  or  in  the  absence 
of  water,  by  the  action  of  dry  ammonia  upon  an  alcohol-ether  solution  of  pyromucyl- 
hydroxamic  acid. 

39  von  Meyer  and  Fischer,  /.  prakt.  Chem.,  [2]  82,  521  (1910). 


2442  LAUDER  W.  JONES  AND  CHARLES  D.  HURD. 

Analyses.  (I)  Prepared  in  the  presence  of  water.  Subs.,  0.1114:  N,  15.9 cc.  (over 
40%  KOH  at  27°  and  737.9  mm.);  (II)  prepared  in  the  absence  of  water;  subs.,  0.2126  : 
N,  27.58  cc.  (17.3°,  and  772.6  mm'.  (15°)).  Calc.  for  CioHuOsN,;  N,  15.49.  Found- 
(I)  15.41,  .(II)  15.30. 

Benzoyl  Ester,  C4H3O.CO.NH.OCO.C«Hi.— Pickard  and  Neville39  stated  that  this 
derivative  "is  precipitated  when  an  aqueous  solution  of  the  hydroxamic  acid  is  shaken 
with  the  calculated  quantity  of  benzoyl  chloride,  and  sodium  acetate."  Potassium 
hydroxide  was  found  to  be  far  superior  to  sodium  acetate.  Three  g.  of  pyromucyl- 
hydroxamic  acid,  and  1.3  g.  of  potassium  hydroxide  were  dissolved  in  20  cc.  of  water, 
and  2.7  cc.  of  benzoyl  chloride  was  added  in  4  portions.  A  quantitative  yield  of  the 
benzoyl  ester  resulted.  After  recrystallization  from  alcohol,  the  compound  melted  at 
140°.«0 

Preparation  of  Salts. — The  following  general  method  was  employed  in  the  prepara- 
tion of  the  potassium  and  the  sodium  salts  of  the  esters.  Alcoholic  solutions 
of  sodium  ethylate,  or  of  potassium  ethylate  were  added  to  concentrated 
alcoholic  solutions  of  the  esters.  The  salt  usually  precipitated  at  once.  It  was  found 
advantageous  to  add  the  alcoholate  in  a  slight  excess.  Three  or  four  volumes  of  ether 
were  added  to  effect  a  complete  separation  of  the  salt. 

To  prepare  the  silver  salts,  it  was  necessary  only  to  add  a  solution  of  silver  nitrate 
in  water,  to  an  aqueous  solution  of  the  potassium  salt.  In  most  cases  this  could  be 
done  at  room  temperature,  but  in  a  few  cases  a  lower  temperature  was  required  to 
inhibit  any  hydrolysis. 

Potassium  Salt.  C«H,O.CO.NK.O.CO.C«H6.—  The  appearance  of  the  dry  salt 
was  unchanged  after  8  months.  In  a  small  tube,  it  puffed  at  125°. 

Analysis.  Subs.,0.4337:  KjSO4,  0.1380.  Calc.  for  C12H8O4NK:K,  14.52.  Found: 
14.28. 

Sodium  Salt. — 41This  salt  was  white  when  first  formed,  but  in  3  months  the  color 
was  distinctly  yellow. 

Silver  salt. — The  silver  salt  was  pure  white. 

Analysis.  Subs.,  0.1289:  Ag,  0.0413.  Calc.  for  CnH8O4NAg:  Ag,  31.92.  Found: 
32.04. 

All  of  these  salts  showed  a  decided  tendency  to  undergo  hydrolysis.  The  potassium 
salt,  dissolved  in  cold  water,  gave  a  ferric  chloride  color  test  in  a  very  short  time.  Sim- 
ilarly, a  little  of  the  silver  salt  suspended  in  boiling  water,  caused  a  separation  of  black 
silver,  a  reaction  characteristic  of  monohydroxamic  acids. 

When  a  0.5  M  solution  of  the  potassium  salt  was  warmed  carefully  to  about  70°, 
crystals  were  precipitated  which  were  unmistakably  identified  as  the  benzoyl  ester. 
By  careful  application  of  heat,  the  filtrate  gave  a  still  more  abundant  yield  of  the  same 
ester.  If  the  filtrate  from  this  precipitate  was  heated  to  boiling,  a  red  resinous  mass 
accompanied  by  the  evolution  of  much  carbon  dioxide,  was  formed.  This  was  dried, 
and  then  recrystallized  twice  from  a  mixture  of  alcohol  and  ether.  After  this  treat- 
ment, it  was  still  colored.  The  material  darkened  at  180°,  and  melted  at  210°  with 
decomposition.  This  is  presumably  sym.  difuryl  urea,  although  enough  was  not  obtained 
for  analysis. 

If  the  solution  of  the  potassium  salt  was  heated  immediately  to  boiling,  the  same 
resinous  mass  was  produced,  but  the  separation  of  the  benzoyl  ester  did  not  occur. 
Acetyl  Ester,  C4H3O. CO. NH.O.COCH3.— Three  g.  of  pyromucyl-hydroxamic  acid 

39  Re/.    24,  p.    848. 

40  That  obtained  by  Pickard  and  Neville  melted  at  134°. 

41  This  salt  was  previously  prepared  by  Pickard  and  Neville. 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.  2443 

and  an  excess  (3  cc.)  of  acetic  anhydride  were  warmed  until  solution  occurred.  The 
excess  of  anhydride  was  evaporated  in  a  vacuum  desiccator.  The  white  crystalline 
mass  was  pressed  upon  a  porous  plate,  and  recrystallized  from  water.  It  melted  at 
95-96°.  This  ester  is  soluble  in  alcohol,  in  ethyl  acetate,  in  chloroform,  in  acetone,  in 
hot  benzene  and  in  hot  water.  It  is  insoluble  in  ether  and  in  ligroin. 

Analyses.  Subs.,  0.3526,  0.2920:  N,  26.1  cc.  (over  40%  KOH  at  24.5°  and  740.3 
mm.  (26.5°)),  21.6  cc.  (26°  and  743.8  mm.).  Calc.  for  C7H7O4N  :N,  8.28.  Found: 
8.09,  8.08. 

Potassium  salt. — The  appearance  of  this  salt  was  unchanged  after  standing  for 
8  months. 

Analysis.  Subs.,  0.3325:  K2SO4,  0.1403.  Calc.  for  C7H6O4NK :  K,  18.87.  Found: 
18.98. 

Sodium  salt. — Alcoholysis  of  the  salt  could  not  be  prevented,  even  when  it  was 
prepared  at  0°.  The  salt  of  pyromucyl-hydroxamic  acid  was  shown  to  be  present 
when  it  was  treated  with  a  solution  of  ferric  chloride,  by  the  appearance  of  a  deep 
purple  color.  It  was  expected,  therefore,  that  the  percentage  of  sodium  in  the  sample 
would  be  higher  than  that  required  by  the  sodium  salt  of  the  acetyl  ester  of  pyromucyl- 
hydroxamic  acid. 

Analyses.  Subs.,  0.2667,  0.1064:  Na2SO4,  0.1133,  0.0436.  Calc.  for  C7H6O4NNa: 
Na,  12.14.  Found:  13.75,  13.27. 

A  still  higher  sodium  content  was  found  when  methanol,  at  0°,  replaced  ethyl 
alcohol  in  its  preparation.  After  3  months  the  salt  was  bright  yellow  in  color. 

Analysis.     Subs.,  0.1032:  Na2SO4,  0.0470.     Found:  Na,  14.75. 

Silver  salt. — It  was  necessary  to  prepare  this  derivative  at  0°  When  the  salt  was 
prepared  at  room  temperature,  hydrolysis  to  give  the  monohydroxamic  acid  was  in- 
dicated by  the  formation  of  a  black  precipitate  of  metallic  silver. 

Analysis.  Subs.,  0.0982:  Ag,  0.0382.  Calc.  for  C^eO^Ag:  Ag,  39.09.  Found: 
38.90. 

Both  the  rearrangement  and  the  hydrolysis  of  these  salts  were  perfectly  analogous 
to  the  behavior  shown  by  the  salts  of  the  benzoyl  ester;  except  that  in  this  case  the 
tendency  to  hydrolyze  appeared  greater. 

4.  Thenhydroxamic  Acid. 


jj  CO .  NHOH. 


\ 

•      S 

First  Method. — A  solution  of  free  hydroxylamine  in  methanol  was  prepared  by 
mixing  Solutions  A,  and  B,  composed,  respectively  of,  4.90  g.  of  hydroxylammonium 
chloride  in  50  cc.  of  methanol,  and  35  cc.  of  methanol  to  which  1.67  g.  of  sodium  had 
been  added.  Sodium  chloride  was  removed  by  filtration. 

Nine  and  six-tenths  g.  of  thenoic  ethyl  ester,  C4H3S — CO.OC2H5,  previously  purified 
by  distillation  in  vacua,  was  added  to  the  alcoholic  solution  of  hydroxylamine,  followed 
by  one  mol  of  sodium  methylate  (1.42  g.  of  sodium  in  30  cc.  of  methanol),  and  the  mix- 
ture was  allowed  to  stand  overnight.  Then  5  cc.  of 'cone,  hydrochloric  acid  was  used 
to  precipitate  the  sodium  as  sodium  chloride.  The  solvent  distilled  in  vacua,  after 
filtration  to  remove  the  salt,  left  a  thick  liquid  which  was  placed  in  a  vacuum  des- 
iccator to  crystallize.  The  solid  obtained  in  this  way,  crystallized  from  water,  melted 
at  105-113°.  Recrystallization  from  toluene  resulted  in  pure  material,  m.  p.  123-124.5°. 

A  water  solution  of  tVienhvoVoyamio  arin"  is  arid  to  litmus.      With    ferric    chloride 


2444  LAUDER  W.  JONES  AND  CHARLES  D.  HURD. 

and  copper  acetate,  it  reacts  in  the  normal  manner,  to  give  respectively,  a  purple  colored 
liquid,  and  a  grass-green  copper  salt.  The  acid  is  soluble  in  alcohol,  in  hot  toluene, 
in  hot  benzene,  in  chloroform,  and  in  water.  It  is  insoluble  in  ether  and  in  ligroin. 
With  isatin,  and  warm  sulfuric  acid  the  red  color  characteristic  of  thiophene  derivatives 
is  produced. 

Analysis.  Subs.,  0.2259:  N,  19.12  cc.  (over  40%  KOH  at  18.5°  and  757.8  mm.). 
Calc.  for  CiH,OiNS:  N,  9.78.  Found:  9.74. 

Isolation  of  thenhydroxamic  acid  through  the  medium  of  the  copper  salt  and 
hydrogen  sulfide  was  found  to  be  successful,  but  the  procedure  is  not  to  be  recommended. 

The  Preparation  of  a-Th  noyl  Chloride,  C^aS.COCl.— Thenoyl  chloride  has 
always  been  prepared  from  thenoic  acid  by  the  action  of  phosphorus  pentachloride.48 
A  much  simpler,  and  smoother  preparation  follows  if  thionyl  chloride,  SOClj,  is  employed 
instead  of  the  phosphorus  compound. 

Six  g.  of  a-thenoic  acid  was  warmed  with  16  cc.  of  thionyl  chloride  until  the  gas 
evolution  showed  that  the  reaction  was  complete,  when  the  two  chlorides  were  separated 
by  fractional  distillation.  Thenoyl  chloride  all  distilled  between  206°  and  210°;  yield, 
6g. 

a-Thenhydroxamic  Acid.  Second  method. — A  solution  of  0.3  g.  of  sodium  carbonate, 
and  0.2  g.  of  hydroxylammonium  chloride  in  2.5  cc.  of  water  was  shaken  with  0.3  g. 
of  thenoyl  chloride.  Di-thenhydroxamic  acid  CiHtS.CO.NH.O.CO.CiHiS  (see  p. 
2445)  precipitated  from  the  solution,  whereas  thenhydroxamic  acid  did  not.  To  recover 
the  latter,  the  filtrate  was  made  slightly  acid  with  acetic  acid,  and  treated  with  copper 
acetate  solution.  The  light  green  copper  salt  precipitated,  although  the  green  color 
of  the  solution  showed  that  it  possessed  a  rather  high  degree  of  solubility.  The  filtrate 
still  gave  an  intense  ferric  chloride  reaction. 

The  precipitate  of  di-thenhydroxamic  acid  was  recrystallized  from  alcohol  and 
water.  It  melted  at  105-107°.  We  did  not  try  to  prepare  thenhydroxamic  acid  by 
our  new  method,  viz.,  by  the  action  of  free  hydroxylamine  and  a  benzene  solution  of 
thenoyl  chloride.  No  side  reactions  would  be  anticipated  in  this  case. 

Ammonium  Salt.  (C4H,S.CO.NH.O— )2H.NH4.— This  difficultly  soluble  acid  salt 
was  prepared  in  exactly  the  same  way  as  the  similar  furan  salt,  (p.  2441)  and  showed 
the  similar  property  of  dissolving  either  in  ammonia,  or  in  hydrochloric  acid.  For  analy- 
sis, the  salt  was  precipitated  from  an  alcohol-ether  solution  bf  thenhydroxamic  acid  by 
dry  ammonia.  It  melted,  with  decomposition,  at  142-143°. 

Analysts.  Subs.,  0.1172:  N,  13.95  cc.  (21°  and  769  mm.  (20°)).  Calc.  for  do- 
HtfQiNaSi:  N,  13.85.  Found:  13.75. 

Benzoyl  Ester,  C4HSS.CO.NH.O.CO.C«H5. — Two  g.  of  thenhydroxamic  acid,  and 
0.8  g.  of  potassium  hydroxide  were  dissolved  in  10  cc.  of  water.  This  solution,  agitated 
with  1.7  cc.  of  benzoyl  chloride,  gave  a  precipitate  which  was  recrystallized  from  alcohol. 
The  needle  shaped  crystals  so  obtained  melted  sharply  at  143-144°,  with  decomposi- 
tion. It  is  soluble  in  alcohol,  in  acetone  and  in  ethyl  acetate,  and  is  insoluble  in  ligroin, 
or  in  cold  water. 

Analysis.  Subs.,  0.4336  g.:  N,  21.97  cc.  (at  21°  and  758.6  mm.  (at  19°)).  Calc. 
for  C,2H9O3NS:  N,  5.67.  Found:  5.77. 

Potassium  Salt. — The  general  method  described  upon  p.  2422,  was  used  also  to 
prepare  the  salts  in  this  series."  The  potassium  salt  was  pure  white.  When  it  was 
heated  in  a  small  dry  tube,  it  became  yellow  at  121°  and  decomposed  with  a  faint 
puff  at  125-127°. 

Analysis.  Subs.,  0.5313:  K2SO«,  0.1626.  Calc.  for  Ci,HsO»NSK:  K,  13.71. 
Found:  13.73. 

"  V.  Mever  and  Kreis,  Ber.,  16,  2174  (1883);  Peter.  B.-r  .  18,  543  (1- 


REARRANGEMENTS  OP  NEW  HYDROXAMIC  ACIDS.  2445 

Sodium  Salt. — When  slowly  heated,  the  sodium  salt  decomposed  mildly  between 
155°  and  160°. 

Analysis.  Subs.,  0.2388:  Na2SO4,  0.0631.  Calc.  for  Ci2H8O3NSNa:  Na,  8.54. 
Found:  8.55. 

Silver  Salt.— The  silver  salt  decomposed  between  163°  and  168°.  Above  this 
temperature  thienyl  isocyanate  distilled  from  the  tube. 

Analysis.  Subs.,  0.2364:  Ag,  0.0723.  Calc.  for  C^HgOsNSAg :  Ag,  30.47.  Found 
30.58. 

Rearrangement  of  the  Salts. — A  0.5M  solution  of  the  potassium  salt  in  water  was 
boiled.  The  solution  darkened,  and  di-thienyl  urea  precipitated  as  a  gray- violet  crystal- 
line mass.44  It  was  collected  and  recrystallized  from  acetic  acid.  The  melting  point 
was  224-225°. 

The  nitrate  was  acidified  and  the  precipitate  obtained  was  crystallized  fractionally 
from  dilute  alcohol.  Crystals  melting  at  140-144°  separated  at  first.  This  material 
was  the  benzoyl  ester,  which  must  have  been  formed  by  hydrolysis  of  the  salt.  Benzoic 
acid  was  left  in  the  filtrate.  The  ratio  of  the  urea  to  the  benzoyl  ester  was  about  4:1. 

Acetyl  Ester,  C4H3S.CO.NH.O.CO.CH3. — Three-tenths  g.  of  pure  thenhydroxamic 
acid  was  warmed  in  an  open  glass  dish  with  0.2  g.  of  acetic  anhydride.  As  soon  as 
solution  had  taken  place,  the  dish  was  placed  in  a  vacuum  desiccator  to  remove  the 
excess  of  anhydride.  The  white  solid  obtained  was  recrystallized  from  benzene.  The 
melting  point  was  sharp  at  96.5-97  ° ;  yield,  quantitative.  The  ester  is  soluble  in  alcohol, 
in  ethyl  acetate,  and  in  hot  benzene,  but  is  insoluble  in  cold  benzene  and  in  ligroin. 

Analysis.  Subs.,  0.3242:  N,  21.47  cc.  (over  40%  KOH  at  17.8°  and  760.3  mm. 
(15°)).  Calc.  for  C7H7O3NS:  N,  7.57.  Found:  7.66. 

Potassium  Salt. — No  precautions  were  necessary  to  prepare  the  potassium  salt 

Analysis.  Subs.,  0.3099:  K,SO4,  0.1215.  Calc.  for  C6H6O3NSK:  K,  17.51.  Found 
17.49. 

Sodium  Salt. — Ice-cold  solutions  were  essential  in  the  preparation  of  the  sodium 
salt.  Otherwise,  alcoholysis  to  yield  the  monohydroxamic  acid  occurred. 

Analysis.  Subs.,  0.0609:  Na2SO4,  0.0209.  Calc.  for  C7H6O3NSNa:  Na,  11.10. 
Found:  11.11. 

Silver  Salt. — Because  of  hydrolysis,  a  water  solution  of  the  sodium  salt  could  not 
be  used  to  prepare  the  silver  salt.  A  black  precipitate  of  silver  always  resulted.  With 
the  potassium  salt,  however,  the  preparation  was  entirely  successful. 

Analysis.  Subs.,  0.1481:  Ag,  0.0548.  Calc.  for  C7H6O3NSAg:  Ag,  36.94.  Found: 
37.00. 

These  salts  all  puffed  at  a  comparatively  high  temperature.  A  pronounced  odor 
of  thienyl  isocyanate  was  always  noticed.  When  water  solutions  of  the  salts  were 
boiled,  di-thienyl  urea  separated  instantly.  However,  this  was  always  accompanied 
by  an  unavoidable  hydrolysis  to  form  the  acetyl  ester  and  a  second  hydrolysis  to  give 
thenhydroxamic  acid. 

Thenoyl  Ester,  (Di-thenhydroxamic  Acid),  C4H3S.CO.NH.O.CO.C4H3S. — One  prep- 
aration of  this  ester  (Cf.  p.  2444)  which  resulted  in  the  high-melting  modification  (see 
below)  has  already  been  described. 

Three  g.  of  thenhydroxamic  acid,  and -1.18  g.  of  potassium  hydroxide  were  dis- 
solved in  15  cc.  of  water.  The  ice-cold  mixture  was  treated  with  3  portions  (1  g.  each) 

44  Sym.  di-thienyl  urea  was  found  by  Curtius  and  Thyssen2a  to  be  gray-violet  in 
color,  even  after  7  recrystallizations  from  solvents  with  animal  charcoal;  m.  p.  224°. 


2446  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

of  thenoyl  chloride.  A  precipitate  which  weighed  2.7  g.  was  collected ;  m.  p.  between 
80°  and  88°. 

The  filtrate  was  found  to  be  acid  in  reaction,  and  to  contain  some  unchanged 
thenhydroxamic  acid.  It  was  therefore  made  slightly  alkaline  with  sodium  hydroxide 
and  treated  with  2  cc.  of  thenoyl  chloride.  The  resulting  precipitate  melted  at  90- 
100°  and  weighed  1.4  g.  When  the  filtrate  was  acidified,  an  appreciable  quantity  of 
thenoic  acid  separated. 

The  crude  precipitates,  (m.  p.  80-100°)  were  combined  and  recrystallized  from 
benzene.  Crystals  which  melted  between  83°  and  86°  were  obtained.  Later  a  re- 
determination  of  the  melting  point  of  this  same  sample  indicated  that  a  transformation 
to  a  higher-melting  modification  had  taken  place.  The  melting  point  ranged  from  100° 
to  104°. 

When  alcohol  was  used  as  the  solvent,  the  high  melting  modification  separated  first. 
There  was  an  indication  of  softening  at  95°,  but  the  melting  point  at  102-104°  was 
quite  distinct. 

Both  of  these  compounds  responded  to  all  the  reactions  expected  of  di-thenhydrox- 
amic  acid.44  They  both  formed  salts;  neither  one  gave  a  color  test  with  ferric  chloride, 
but  after  hydrolysis  both  showed  an  intense  purple  color  with  this  reagent.  The  purest 
sample  of  the  high-melting  form  melted  at  105-107°.  Its  isomer  melted  at  83-86°. 
Both  were  soluble  in  alcohol,  in  ethyl  acetate,  and  in  hot  benzene.  In  water  and  in 
ligroin  they  were  insoluble. 

Analyses.  (I)  Low-melting  modification;  subs.,  0.3339:  N,  16.90  cc.  (16.5°  and 
762.0  mm.);  (II)  high-melting  modification;  subs.,  0.4288:  N,  19.60  cc.  (18.5°  and  769.1 
mm.  (16°)).  Calc.  for  CioH7O8NSj:  N,  5.53.  Found:  (I)  5.90,  (II)  5.35. 

Potassium  Salt.  C^S.CO.NK — O.CO.C4HsS. — The  salts  were  all  prepared 
from  di-thenhydroxamic  acid  melting  at  102-104°  In  a  small  tube,  the  temperature 
of  decomposition  of  the  potassium  salt  was  122°. 

Analysis.  Subs.,  0.1988:  KaSO4,  0.0584.  Calc.  for  C.oHeO^NSjK:  K,  1342. 
Found:  13.18. 

Sodium  Salt. — There  was  no  evident  alcoholysis,  when  this  last  was  prepared  at 
room  temperature.  At  142°  the  dry  salt  decomposed. 

Analysis.  Subs.,  0.0797:  NajSO4,  0.0206.  .Calc.  for  C10H6OjNS,Na:  Na,  8.36. 
Found:  8.37. 

Silver  Salt. — An  abundant  white  precipitate  of  the  silver  salt  of  di-thenhydroxamic 
acid  resulted  when  aqueous  solutions  of  the  potassium  salt  and  silver  nitrate  were 
mixed.  It  decomposed  at  155°. 

Analysis.  Subs.,  0.1253 :  Ag,  0.0376.  Calc.  for  C,0HeO,NSjAg:  Ag,  29.96.  Found : 
30.01. 

When  boiled  with  water,  both  the  potassium  and  the  sodium  salts  gave  a  dense 
precipitation  of  sym.  di-thienyl  urea.  Water  solutions  of  the  pure  salts  did  not  readily 
undergo  hydrolysis  or  rearrangement. 

5.  Benzhydroxamic   Acid. 

The  new  method  of  preparation  of  hydroxamic  acids,  (see  p.  2430)  namely, 
by  the  use  of  the  acid  chloride  in  benzene,  was  successfully  employed  in  the  preparation 
of  -benzhydroxamic  acid  from  benzoyl  chloride. 

Hirst  Method. — Six  and  five-tenths  g.  of  benzoyl  chloride  was  dissolved  in  70  cc. 
of  dry  benzene.  Upon  the  addition  of  3.3  g.  of  free  hydroxylamine  a  dense  precipitate 
of  benzhydroxamic  acid  was  formed.  The  reaction  mixture  was  shaken  vigorously, 

44  Lessen.   Ann.,  281,  289   (1894). 


REARRANGEMENTS  OF  NEW  HYDROXAMIC  ACIDS.         2447 

and  then  set  aside  for  a  few  hours  until  the  odor  of  benzoyl  chloride  had  disappeared. 
Less  than  half  a  gram  of  benzhydroxamic  acid  was  recovered  from  the  benzene  filtrate. 
One  recrystallization  of  the  solid  from  hot  toluene  removed  hydroxylammonium  chloride 
and  yielded  a  pure  product,  m.  p.  124°.  This  is  identical  with  the  material  described  by 
Lessen.29  No  evidence  of  the  higher  melting  di-benzhydroxamic  acid  was  observed. 

Second  Method. — Benzhydroxamic  acid  was  also  prepared  in  excellent  yields,  from 
benzoyl  chloride,  dissolved  in  organic  solvents,  with  hydroxylammonium  chloride 
instead  of  free  hydroxylamine.  An  intimate  mixture  of  anhydrous  sodium  carbonate 
(2.1  g.)  and  hydroxylammonium  chloride  (1.4  g.)  was  suspended  in  50  cc.  of  ether. 
When  2.8  g.  of  benzoyl  chloride  was  added  there  was  little  action,  but  it  became  more 
vigorous  when  3.5  cc.  of  water  was  added.  In  about  half  an  hour  the  reaction  was 
complete.  The  ether  solution  was  filtered  into  a  distilling  flask,  and  most  of  the  solvent 
was  removed.  When  this  residue  was  cooled,  an  abundant  crystalline  mass  precipitated. 
This  was  filtered,  washed  with  a  little  ether,  and  pressed  upon  a  porous  plate.  The 
benzhydroxamic  acid  melted  at  124-125°  without  further  purification.  Yield,  nearly 
quantitative. 

Similarly,  benzhydroxamic  acid  was  obtained  in  quantitative  yields  when  pyridine 
was  substituted  for  sodium  carbonate.  Benzene  was  used  instead  of  ether  in  this  case. 

Thenoyl  Ester  of  Benzhydroxamic  Acid,  C6H5.CO.NH.O.CO.C4H3S. — Two  and  a 
half  g.  of  benzhydroxamic  acid  dissolved  in  25  cc.  of  water  was  neutralized  with  0.7  g. 
of  potassium  hydroxide.  Three  portions  of  1  g.  each  of  thenoyl  chloride  were  added 
to  this  solution.  The  precipitate  was  filtered,  and  washed  with  water;  yield,  2  g. 
When  it  was  recrystallized  from  ethyl  acetate,  it  gave  white  needles  which  melted  at 
133.0-133.5°.  The  ester  is  soluble  in  alcohol,  in  acetone,  in  ethyl  acetate  and  in  hot 
benzene.  It  is  insoluble  in  cold  benzene,  in  ligroin  and  in  water. 

Analysis.  Subs.,  0.1547:  N,  7.70  cc.  (over  40%  KOH  at  15°  and  763  mm.).  Calc. 
for  Ci2H9O3NS:  N,  5.67.  Found:  5.85.  „ 

Potassium  Salt.  C6H5.CO.NK.O.CO.C4H3S. — When  0.32  g.  of  the  thenoyl  ester 
was  dissolved  in  a  mixture  of  2  cc.  of  alcohol  and  1  cc.  of  ether,  the  potassium  salt  was 
precipitated  by  the  addition  of  0.7  cc.  of  an  alcoholic  solution  of  potassium  hydroxide 
(0.08  g.  KOH).  Five  cc.  of  ether  caused  further  precipitation. 

A  water  solution  of  this  salt  became  turbid  in  a  short  time,  when  left  at  room 
temperature.  When  the  solution  was  boiled,  a  crystalline  precipitate  of  sym.  diphenyl 
urea,  m.  p.  236-238°,  was  formed. 

The  dry  potassium  salt  puffed  vigorously  at  135-140°,  providing  the  tube  contain- 
ing it  was  thrust  into  a  bath  previously  heated  to  that  temperature.  However,  when 
the  tube  was  gradually  warmed,  a  mild  decomposition  took  place.  There  was  no 
noticeable  action  until  160°,  although  phenyl  isocyanate  was  undoubtedly  being  evolved 
at  a  temperature  somewhat  below  that. 

Analysis.  Subs.,  0.1788:  K2SO4,  0.0538.  Calc.  for  Ci2H8O3NSK:  K,  13.70. 
Found:  13.50. 

Silver  Salt. — When  silver  nitrate,  in  water  solution,  was  added  to  a  solution  of 
the  potassium  salt  in  water,  a  voluminous  white  precipitate  of  the  silver  salt  resulted. 
It  blackened  near  165°. 

Analysis.  Subs.,  0.0897;  Ag,  0.0274.  Calc.  for  Ci2H8O3NSAg :  Ag,  30.47.  Found: 
30.54. 

Summary. 

An  interpretation  of  the  mechanism  of  the  Beckmann  rearrangement 
has  been  proposed,  based  upon  the  modern  conception  of  chemical  bonds 


2448  LAUDER  W.  JONES  AND  CHARLES  D.  KURD. 

and  electrons.  The  transfer  of  electrons  for  all  stages  in  the  process  has 
been  pictured  in  a  detailed  manner. 

The  following  hypothesis  has  been  advanced:  the  relative  ease  of  re- 
arrangements of  the  Beckmann  type  is  dependent  upon  the  tendency  for 
the  radical  R  in  the  univalent  nitrogen  derivative,  e.  g.,  (R.CO.N),  to 
exist  as  a  free  radical. 

The  hypothesis  was  tested  successfully  with  the  sodium  and  the  potas- 
sium salts  of  the  acyl  esters  both  of  diphenylacethydroxamic  acid  and  of 
triphenylacethydroxamic  acid.  Rearrangement  of  the  salts  in  solution 
was  found  to  be  more  reliable  for  purposes  of  comparison  than  rearrange- 
ment of  the  solid  salts.  In  agreement  with  the  hypothesis,  the  relative 
ease  of  rearrangement  was  greater  with  triphenylacethydroxamic  acid 
derivatives  than  with  the  similar  compounds  in  the  diphenyl  series.  When 
water  solutions  of  the  salts  in  the  triphenyl  series  were  heated,  the  pro- 
duct of  rearrangement  was  triphenylmethyl  isocyanate,  and  not  sym. 
bi-triphenylmethyl  urea.  This  is  a  singular  fact.  The  phenomenon  of 
chromo-isomerism  was  displayed  by  the  silver  salts  of  the  diphenyl  series, 
as  well  as  those  of  the  triphenyl  series. 

Diphenyl  ketene  and  hydroxylamine  were  found  to  react  readily  in  a 
neutral  solvent  to  form  diphenylacethydroxamic  acid.  Modifications 
of  this  new  reaction  between  ketenes  and  hydroxylamine,  or  substituted 
hydroxylamines,  should  be  valuable  in  future  synthetic  work. 

The  properties  of  pyromucyl-hydroxamic  acid,  and  of  a-thenhydrox- 
amic  acid  have  been  determined.  The  latter  resembles  benzhydroxamic 
acid  very  closely.  The  former  is  similar  to  benzhydroxamic  acid  in  many 
respects,  but  its  derivatives  differ  materially  in  rearrangement.  These 
two  compounds,  which  are  representatives  of  the  furane  and  of  the  thio- 
phene  types,  prepare  the  way  for  further  investigations  of  heterocyclic 
hydroxamic  acids. 


Accepted  by  the  Department  <  f  Chemistry, 
Jum     HUM 


Rearrange 


new  hydroxa 
related  to 


iients  of  some 
flic  acids— 
beterocyclic 


A7E8 


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